Manual for submarine mining (2024)

EDITION OF 1912

WASHINGTON
GOVERNMENT PRINTING OFFICE
1912

War Department,
Document No. 399.
Office of the Chief of Staff.

CONTENTS.

A submarine mine consists of an explosive charge inclosed in awater-tight case, and a firing device, the whole intended to besubmerged in a waterway which it is desired to close against thepassage of an enemy’s vessels.

With respect to the position of the case containing the explosive,submarine mines are of two classes, buoyant and ground.

In the buoyant mine, the case contains the explosive and the firingdevice, and has such excess of buoyancy that it would float were it notheld below the surface by a mooring rope and an anchor. The submergenceis such that, while the mine would be struck by the hull of a passingvessel, it is not so near the surface as to be seen.

Buoyant mines may be planted and operated successfully in water 150feet deep. They should not, in general, be used where the depth ofwater is less than 20 feet.

In the ground mine, the case contains the explosive and the firingdevice, and is heavier than the displaced water; it therefore restsupon the bottom and requires no anchor. Ground mines are not used wherethe depth of water exceeds 35 feet.

With respect to the means used to fire them, mines may be classed asmechanical and electrical.

Electrical mines are, in turn, of two general classes, controllable—inwhich the firing device is under control after the mine has been fixedin position; and noncontrollable—in which no such control is had.

Mechanical and noncontrollable electrical mines are intended to befired only by the blow of a passing vessel. When once in position they[Pg 8]are dangerous alike to friend and foe, while controllable minesmay instantly be made safe for friendly vessels or as quickly madedangerous to vessels of the enemy.

Controllable electrical mines are arranged so as to give a signalto the operator when they are struck. They may be set to fireautomatically when struck or tampered with, or may be fired at the willof the operator. In the latter case the firing may be delayed, in whichcase the operator fires the mine some short interval after the signalindicates that it has been struck; or by observation, in which case hefires it after the position-finding system shows that the vessel hascome within the mine’s destructive radius.

LOCATION OF MINES.

The considerations involved in the location of mines are of two generalclasses, tactical and local.

Tactical considerations deal with the position of mines with referenceto the other defenses. Local considerations deal with the width anddepth of the channel, the swiftness of the current, the variation ofthe tide, and the relative importance of the harbor.

Where ordinary ship channels are unobstructed it is possible for modernbattleships, with their high speed and heavy armor, to run by shorebatteries, at least in the night or during a fog; hence the defense ofsuch channels should not be left to guns alone.

On the other hand, where mines are unprotected by the fire of shorebatteries it is possible for an enemy to remove or disable them.

Therefore guns and mines, the two elements of the fixed defenses of aharbor, are mutually dependent, and when the location of one has beendecided upon that of the other must conform thereto.

Within the zone between 4,000 and 8,000 yards of the main defense thefire of heavy guns is destructive for warships, yet the latter are atsuch a distance that their rapid-fire guns will be of little effectagainst the batteries.[Pg 9]

Moreover, at 4,000 yards vessels are just beyond the inner limit ofmortar fire.

If possible, therefore, hostile vessels should be held in this zone bysome obstacle. Such obstacle is afforded by a mine field.

On the other hand, attacks upon a mine field are most liable to be madeby small boats at night. If the mine field be at too great a distancefrom the defenses, these boats will not be revealed by the minesearchlights. Furthermore, for protection against such attacks, thedefense relies upon rapid-fire guns of relatively limited range.

Due to the above considerations the outermost mines are usually placedbetween 3,000 and 4,500 yards from the main defense.

In general, there should be in each main channel at least three linesof mines.

ELEMENTS OF A MINE SYSTEM.

The elements of a mine system are:

1. The mining casemate, consisting typically of four rooms:(1) The operating room, containing the power panel and the operatingboards; (2) the engine room, containing the engine and the generator;(3) the battery room, containing the storage battery; and (4) thesleeping room for the personnel.

2. The multiple cables, 7 and 19 conductor, leading from thecasemate out to the distribution boxes, one of which is in the centerand rear of each group of mines.

3. The single-conductor cables, radiating to the front from thedistribution boxes, one leading to each mine.

4. The mines, in groups of 19 or less, extending across thewaterway to be defended, planted approximately 100 feet apart andanchored so as to have a submergence of about 10 feet at low water. Thegroups are numbered 1, 2, 3, etc., from left to right of the observerstationed in rear of the line, and the mines in each group are numberedsimilarly, No. 1 being on the left, No. 10 in the center, and No. 19 onthe right.[Pg 10]

The groups composing a line of buoyant mines are not usually plantedin prolongation of each other, but with a space for the passage offriendly vessels, and also for the movement of the planter when atwork upon adjacent groups. Groups of ground mines may be placed inprolongation of each other or between the groups of buoyant mines, asthey will always be below the hulls of passing vessels.

5. The mine planters and other boats with the necessaryequipment for planting and maintaining the planted mines.

6. The range-finding system, the same as or similar to thatused for the guns, enabling accurate plotting of the positions of theindividual mines, and consequently permitting vessel tracking andobservation firing.

7. The searchlights, for illuminating the mine fields at night.

8. The rapid-fire guns, for the protection of the mine fields.

The generating set.—This consists of a D. C., shunt-woundgenerator driven by a kerosene oil engine, or of a direct-connectedgasoline set. (For method of operation of a Hornsby-Akroyd oil engine,see Appendix 2.)

The storage battery.—This is a 40-cell chloride accumulator,with a normal charge and discharge rate of 5 amperes. The voltage maybe taken at 2 volts per cell; the internal resistance is negligible.Directions for setting up, care, and usage of the storage battery aregiven in Appendix 3. The 5-ampere battery isthe standard equipment at the present time, but the new installationswill have batteries with a normal charge and discharge rate of 15 amperes.

The motor-generator, D. C.-A. C.—This is a D. C.-A. C.(60-cycle, single phase) machine, running on D. C. voltage (80-110)and designed to give one-half kilowatt at 80 volts. To insure againstbreakdown two of these motor-generators are supplied to each casemate.

Starting switch.—This is a 4-point lever switch and is used tostart the motor-generator and to accelerate it to full speed. To insureagainst breakdown two of these motor-generators circuit to the fourthpoint. Resistances are connected between the points, as shown infigure 1. The contact made at point 1 is notbroken as the lever is moved to its successive positions. It is seenthat the total resistance is 8 ohms; it is all in the armature circuitwhen the switch blade is in the first point; 4 ohms when in thesecond point; 2 ohms when in the third point; none when in the fourthpoint. The operation of closing the lever short circuits in turn theresistances 4, 2, and 2.[Pg 12]

The casemate transformer.—This is a step-up transformer, of theoil-insulated core type, and is rated at 60 cycles, 500 watts, 80 voltsprimary and 500 volts secondary, when carrying full load.

The power panel.—This panel is shown in figure 2, its wiring diagram in figure 18 at the endof the book. It consists of an enameled slate panel upon which theapparatus is mounted. It is 32 inches wide, 69 inches high, and is setup with its face 34 inches from the wall in rear.

[Pg 13]Across the top are two lamps, a double circuit breaker, a D. P. D. T.switch, and a single circuit breaker. Below these there are an ammeter,an A. C. voltmeter, and a D. C. voltmeter. Below the ammeter is abattery rheostat and below the D. C. voltmeter a field rheostat. On abracket at the side there is a mil-ammeter, with a 16 c. p., 110-voltlamp in series with it.

The remaining switches, receptacles, and attachments are sufficientlywell indicated in the figures.

Switch No. 1 controls the lamps at the top of the board. When it is up,they are supplied from an external source of power. When it is down,they are supplied from the storage battery.

The D. C. terminals are all carried to one terminal bar, the A. C.terminals to another. All terminals and all switches are labeled.

Provision is made for energizing the D. C. busses:

(a) From an external source of power: Close single circuitbreaker and close switch No. 2 to the right—facing the board.

(b) From the casemate generator: Close single circuit breakerand close switch No. 2 to the left—facing the board.

(c) From the storage battery: With switch No. 2 open, closedouble circuit breaker.

Feeder switches are plainly marked. The D. C. switches supply power asfollows:

No. 3. When up, supplies the operating boards (negative pole to boards,positive to earth); when down, it is spare.

No. 4. When up, supplies motor-generator No. 1; when down,motor-generator No. 2.

No. 5. When up, supplies the mine commander’s station.

No. 6. When up, supplies casemate lamps; when down, it does the same,but the power is now drawn from an external source and not from the D.C. busses.

No. 7. When up, grounds the positive bus and connects the negative busthrough the protective lamp and mil-ammeter to the mil-ammeter lead.

The A. C. switches supply power as follows:

No. 8. When up, supplies the operating boards, one pole to boards, the[Pg 14]other to earth through an independent lead; when down, it does thesame, but the side grounded is grounded through a choke coil.

No. 9. When up, energizes the A. C. busses from motor-generator No. 1;when down, the A. C. busses from motor-generator No. 2.

No. 10 is spare.

No. 11. When up, supplies power to the primary of the testingtransformer; when down, it is spare.

No. 12. When up, supplies power from the secondary of the testingtransformer to the test fuses.

Voltmeter receptacles and plugs, all of which are properly marked, areprovided for obtaining the reading of the A. C. and D. C. voltages. TheD. C. receptacles are on the right and the A. C. on the left. The firstreceptacle of each set is spare to hold the plugs when the latter arenot in use.

With the D. C. plug:

In the second receptacle, the voltage of the casemate generator isindicated.

In the third receptacle, voltage of external D. C. power.

In the fourth receptacle, voltage of storage battery.

With the A. C. plug:

In the second receptacle, voltage of A. C. power on the busses isindicated.

In the third receptacle, voltage of external A. C. power, if the latteris supplied.

In general, no external A. C. power should be led into the casemate, asthe system would be unsafe, owing to the liability of a “cross.” Thestandard system is perfectly safe, as it is impossible for a mine to befired when the motor-generators are idle.

The double circuit breaker is an ordinary single-coil breaker. Thesingle circuit breaker is an overload and reverse-current circuitbreaker. The reverse-current coil has two windings, one of which isbridged across the power supply, and the other is in series with it. Oncharge, the effect of these coils is differential, and on discharge itis cumulative and will trip the circuit breaker when the current fromthe storage battery exceeds 2 amperes.

[Pg 15]To charge the storage battery:

The operating board.—A front view of this is given infigure 3, its wiring diagram in figure 18at the end of the book. One is required for each group of 19 mines. Itconsists of an iron frame to which are attached a signal block, amaster block, 19 mine blocks (1 for each mine), busses, and a terminalbar with 19 numbered terminals. The frame is 78 inches high by 24inches wide. It should be set up so that its face is 34 inches from thewall in rear.

The signal block (see fig. 18).—This is an enameled slateblock 24 inches wide and 11 inches high, upon which are mounted threebinding posts, three lamps (red, white, and green), a bell and bellswitch, a 90-ohm non-inductive resistance in parallel with the whitelamp, and a 125-ohm resistance in series with the bell. The bindingposts are marked “Earth” or “G.,” “A. C.,” and “D. C.,” respectively.The bell, the 90-ohm non-inductive resistance, and the 125-ohmresistance are so indicated on the figure. The lamps are marked asfollows: Red, “R. L.”; white, “W. L.”; green, “G. L.”

The circuit, under normal conditions, is: From negative D. C. bus onpower panel, to switch 3 closed up, to “operating board” terminal, toD. C. lead, to D. C. post on signal block, through green lamp, to D.C. jaw on master block, to D. C. bus on operating board, through powerswitch P on mine block, through solenoid S, to middle of testing switchT, to upper contact of same, to upper contact of automatic switch A, tomiddle of same, to mine switch M, through same to terminal bar, through19-conductor and single-conductor cables, through mine transformerprimary, to mine case, to ground, to D. C. “earth” terminal on powerpanel, to switch 3, and to positive D. C. bus on power panel.[Pg 16]

Green lamps of 8, 16, and 32 candlepower are supplied. The16-candlepower green lamp glows dimly when 19 mines are connected tothe operating board and all are free from short circuits, grounds,or abnormal resistances. If it should glow abnormally bright, due togrounds, a 32-candlepower lamp should be substituted. If it should glowvery dimly, due to a less number of mines connected, an 8-candlepowerlamp should be used.

A short circuit in a mine circuit causes the green lamp to glow morebrightly.

Breaks in conductors not causing short circuits will not be revealedordinarily by this lamp. To detect breaks, tests of individual minesmust be made.

The red lamp glows and the bell rings when any automatic switch isdown. The circuit under this condition is:

From negative D. C. bus on power panel to switch 3 closed up, to“operating board” terminal, to D. C. lead, to D. C. post on signalblock, through green lamp to D. C. jaw, to D. C. operating board bus,through power switch on mine block whose automatic switch is down,through insulated pin of lower arm of automatic switch, to lower pointof testing switch T, to operating board lamp bus, through bell, 125-ohmresistance and bell switch, and red lamp in parallel, to “earth” post,to earth lead, to D. C. “earth” terminal on power panel, to switch 3,and to positive D. C. bus on power panel.

The resistance of the bell is such that a resistance of 125 ohms mustbe placed in series with it to make the joint resistance of the redlamp-bell circuit so large that if one automatic switch is down it willnot interfere with the tripping of another.

The white lamp, W. L., is in the firing and A. C. testing circuits. The90-ohm resistance is in parallel with this lamp, and in addition toprotecting it from excessive current, serves to keep the firing circuitcomplete should the lamp burn out.

The master block (see fig. 18).—This is an enameled slateblock 6 inches wide by 9½ inches high, upon which are mounted two jawsfor the terminals of a jumper, a testing switch, T. S., and a firingswitch, F. S.

[Pg 17]The testing switch, T. S., is used to determine if the A. C. power beon the signal block. If so, when it is closed the white lamp on signalblock glows. This switch is marked to indicate its “off” and “on”positions. When “on” the circuit is as given in “test of the deliveryof the A. C. power to the operating board,” Chapter VI.

The firing switch, F. S., is used to throw the A. C. power on theoperating board A. C. busses. This is marked to show its “on” and “off”positions. No mine can be fired unless this switch is in its “on”position. When “on” the firing circuit is as follows:

From A. C. bus on power panel to switch 8 closed up, to “operatingboard” terminal, to A. C. lead, to A. C. post on signal block, towhite lamp and resistance in parallel, to A. C. jaw, through firingswitch, F. S., to A. C. bus on operating board, to lower point ofautomatic switch when it is closed down, to middle point of automaticswitch, through mine switch to terminal bar, through 19-conductor andsingle-conductor cables, through mine transformer primary, to minecase, to ground, to A. C. “earth” terminal on power panel, to switch 8,and to other A. C. bus on power panel. The white lamp glows after themine has been fired.

The mine block (see figs. 4 and18).—This consists of an enameled slate block, 6 inches wide and 9½inches high, on which are mounted four switches.

1. The upper switch is the “mine switch.” When it is open thecorresponding mine is cut out and can not be fired. It is placedhorizontally on the blocks of the old model and vertically on those ofthe new model.

2. The right-hand switch, a S. P. S. T. knife switch, is the “powerswitch.” When it is closed the D. C. power is on the block and theautomatic switch will function when the corresponding mine is struck.When it is open the mine can be fired by raising the automatic switchrelease, thus tripping the automatic switch.

3. The central switch is the “automatic switch,” a single-poledouble-throw switch, operated by the plunger of a solenoid. Through its[Pg 18]lower arm there passes an insulated pin which, when the switch is down,makes connection between two contacts to the right and left of this arm.

If for any cause the current through the solenoid rises above that forwhich it is set (normally 0.075 ampere), its plunger is drawn up andthe switch is tripped. Such rise in current is produced when a mine isstruck, the resistance through the circuit-closer circuit being farless than that through the primary coil of the transformer. Such wouldalso be the case when a mine cable is grounded.

When the automatic switch is tripped, the D. C. circuit to the mineis broken at its upper contact (see fig. 18) and D. C. circuit throughred lamp and bell is made through the insulated through pin in thelower arm, thus giving warning. If at the same time A. C. power be onthe busses and the firing switch on the master block be closed, A. C.will be thrown on the mine through the lower contact of the automaticswitch, and the mine will be fired.

Just above the plunger of the solenoid there is a red knob attachedto the tripping bar of the automatic switch release. This enables theautomatic switch to be released by hand in observation firing and intesting.

4. The left-hand switch, a S. P. D. T. switch, is the “testing switch.”It is used to test the automatic switch, which should open when thetesting switch is thrown down. The bell switch should be opened beforethrowing down testing switch. When the testing switch is in thisposition, the circuit being broken at its upper contact, the mine iscut out, and in place of the mine there is thrown in the red lamp ofthe signal block. The resistance of this red lamp is greater than thatof the mine circuit when the mine is struck, so that if the automaticswitch works for the current through the red lamp it will certainlywork for that through the circuit closer when the mine is struck.

The circuit when the testing switch, T, is down and before theautomatic switch drops is: From negative D. C. bus on power panel, toswitch 3 closed up, to “operating board” terminal, to D. C. lead, to D.C. post on signal block, through green lamp, to D. C. jaw, to D. C. buson operating board, through power switch, through solenoid to middle of[Pg 19]testing switch T, to lower point of same, to operating board lampbus L, through red lamp to “earth” post, to earth lead, to D. C.“earth” terminal on power panel, to switch 3, and to positive D. C.bus on power panel. The circuit, when testing switch, T, is down, andafter the automatic switch has dropped, is the same as theabove up to the power switch, then from the power switch through theinsulated pin in the lower part of the automatic switch, to the lowerjaw of the testing switch, and then the same as the circuit above.

A diagram similar to the wiring diagram, figure 18, at the end ofthe book should be made of the power panel and of one of the operatingboards of each casemate and posted in a conspicuous place in thecasemate. Any changes made in the wiring of either of these boardsshould be made immediately on this diagram.

Submarine mine cable, 19-conductor.—This is an armored cableabout 1 inch in diameter and contains 19 insulated single conductors ofNo. 16 American wire gauge wire (51 mils in dia.). The conductors arearranged in two concentric layers around a single central conductor,the inner layer containing 6, the outer 12. One conductor in each layeris distinguished from the rest by some characteristic mark, as a spiralwhite thread, a wrapping of tape, or other easily detected mark. Themarked conductor in the outer layer is No. 1, that in the inner layerNo. 13, and the central conductor is No. 19. The other conductors arenumbered at the shore end of the cable in a clockwise direction; at thedistant end in a contraclockwise direction.

Submarine mine cable, 7-conductor.—In many cases the7-conductor cable now on hand can be used to advantage for mine work,particularly in planting groups which do not require great lengths ofmultiple cable. In all such cases the old grand junction boxes are to beused as distribution boxes, thus providing for separate groups of 7 mines.

Submarine mine cable, single conductor.—This is an armoredcable, about three-fourths inch in diameter, and contains an insulatedconductor made of 7 strands of soft annealed No. 22 American wire gaugecopper wire (25.35 mils in dia.).[Pg 20]

The buoyant mine case.—The service 32-inch pattern is made of10-pound, ¼-inch, open-hearth steel, of great toughness and elasticity,and is thoroughly galvanized. The shell consists of two hemispheres,ribbed and welded together at the equator, thus avoiding all rivets.Every case before it is accepted is tested with an internal hydraulicpressure of 100 pounds per square inch.

The top hemisphere is provided with an external maneuvering ring;the bottom hemisphere has a hole 5½ inches in diameter at the pole.The edge of the hole is reenforced by a welded ring 1½ inches thick;and near it are four bosses, also welded, carrying screw bolts whichproject 2½ inches outside to secure the cap.

The cap consists of a hemisphere of 15-pound, ⅜-inch wrought iron,flanged and dished at the base to fit the case, to which it is attachedby the four bolts already mentioned. They pass through slots in theflange, which is then held in place by shoes and nuts which are keyedon. The water has free access to the chamber inside the cap. The usesof the cap are: To clamp the Turk’s-head of the mine cable, to coverand protect the portion of the core exposed outside the case, and toserve as an attachment for the wire mooring rope.

A hole 1½ inches in diameter at the pole of the cap is connected bymeans of a slot with a 3-inch hole punched through the cap betweentwo of the bails. This arrangement permits the entrance or removalof the Turk’s-head without removing the cap from the mine case. Themooring attachment consists of a ring of 1½-inch wrought iron, havinga hole 2½ inches in diameter, attached to the cap by three bails of1-inch wrought iron permanently double riveted to the sides. The cap isthoroughly galvanized.

[Pg 21]The large hole in the mine case covered by the cap is closed by aplug. The joint is made water-tight by a lead washer jammed betweenthe plug proper and the case and by a coating of red lead or similarwaterproofing material upon the screw threads. In the strong currentsand deep water of some harbors more buoyancy than is possessed by the32-inch case is required. This is obtained by inserting between thehemispheres a cylinder of 20-pound wrought iron which is stiffened byextra welded ribs for the larger sizes. Such cases are designated bythe diameter in inches of a sphere having the same buoyancy. Thus,a No. 40 case is made by inserting a cylinder 32 inches in diameterand 20.4 inches in length between the two hemispheres of a No. 32case; this is sufficient to make the displacement equal to that of aspherical case 40 inches in diameter. In the latest types the cylindersare made of corrugated mild steel of less thickness, which diminishesvery materially the weights of the cases.

The following table exhibits the dimensions and weights of buoyantmines, with trotol fuse cans, complete except the charges and moorings.The actual free buoyancy when planted will be the difference betweenthe displacement and weight as given in the table, reduced by theweight of the charge and of the moorings and cables:

The compound plug, with old model brass fuse can.—A section of[Pg 22]this plug, with the names of all the parts, is shown in figure 5.The brass fuse can is not used when guncotton is used as a priming charge.

The compound plug, with rubber fuse can.—A section of thisplug, with the names of all the parts, is shown in figure 6.

The compound plug, with trotol fuse can.—A section of thisplug, with the names of all the parts, is shown in figure 7.

In each plug the main parts are screwed together and held in place byset-screws. The connection of the compound plug with the mine casemakes an earth plate, of which the electrical resistance in salt wateris about 1 ohm.

The mine transformer (see fig. 8).—This consistsof a cylindrical brass case, which contains the primary and secondary coilsof the transformer and the reactance coil. The transformer is screwedinto the brass collar or the reenforce and in turn has the circuitcloser screwed upon its top. The fuses are attached to the secondaryand are fired when proper voltage is applied to the primary. Theprimary leads are black; those of the secondary are red. The terminal,P′, of the primary coil is left free for the purpose of testing, butwhen preparing the transformer for use it is attached securely to thebinding post, T. The upper terminal, R′, of the reactance is preparedfor attachment to the ball seat of the circuit closer.

The normal circuit is from P, through the primary coil (the resistanceof which is about 2,400 ohms), to the transformer case, and thence toearth. However, when the mine is struck, so as to close the circuitcloser, a parallel circuit is closed through the reactance (theresistance of which is about 130 ohms), thence to the ball seat of thecircuit closer, through the ball and springs to the transformer case,and thence to earth. In this latter case, therefore, the resistance islessened by about 2,300 ohms.

The reactance coil will permit only a small amount of alternatingcurrent to pass through it when the ball is displaced, hence mines maybe fired whether the ball is displaced or not.

[Pg 23]Two fuses are connected in multiple across the ends of the secondaryterminals. These terminals are 10 inches in length, to allow amplemargin for inserting fuses in the primer.

The transformer is of the step-down type and is rated at 22.5 watts, 60cycles, 500 volts primary, and 14 volts secondary.

The mine circuit when normal is such that 80 volts should give only30 mil-amperes, but a mine may be fired even when the circuit is sodefective that 80 volts give 120 mil-amperes.

Furthermore, 150 volts D. C. may be applied to the primary withoutdanger of explosion.

An explosion can not be produced unless the A. C. busses on theoperating board are energized, and as long as the firing switch on themaster block is open, there is no danger from accidental closing ofswitches in making mine tests or from short circuits in the mine.

Note.—In designingthis transformer the following variations were considered: (a)Omitting reactance and tapping to ball seat beyond primary oftransformer; (b) using a condenser; (c) using two setsof fuses, so as to be able to fire with either D. C. or A. C. All wereeliminated, as they impaired either the safety, the simplicity, or theefficiency of the system.

The circuit closer.—This, when used with the buoyant mine,consists of the following parts: The cap, the spring plate, thedistance ring, the steel ball, and the ball seat, which, whenassembled, are mounted on the top of the mine transformer.

The ground mine case.—The form and details of constructionadopted for the service pattern are the following (see fig. 9):The case is cast-iron, in form a segment of a sphere, of which the heightis two-thirds of the radius. The bottom is nearly flat, with a centralsand-hole plug to empty the casting. Six internal radial ribs are addedto give additional supports to the top; the loading hole, 5½ inches indiameter (3 inches in old pattern), is at the pole and is closed by acompound plug. Before acceptance a hydraulic pressure of 100 pounds persquare inch must be borne without developing leakage.[Pg 24]

Only one size of ground mine has been introduced into our service. Thispattern is designed to contain from 200 to 300 pounds of explosiveand to rest on the bottom in water not exceeding 35 feet in depth athigh tide. The dimensions are as follows: Radius of the sphere, 21⁹/₁₀inches; diameter of the base, 40 inches; extreme height, 25 inches;thickness of iron, seven-tenths of an inch; weight, empty in the air,1,355 pounds; when submerged it loses 515 pounds. The capacity of thiscase is about 5 cubic feet.

A mine cap is provided to clamp the Turk’s-head of the mine cable, tocover and protect the portion of the core exposed outside the case,and to serve as an attachment for the mooring and the raising ropes.This cap is held to the mine case by six bolts, and is fitted with tworings, one for attachment of the mooring rope of the circuit-closerbuoy and the other for attachment of the raising rope.

The compound plug, ground mine.—This is similar to the compoundplug for buoyant mines. The circuit closer is placed in a buoy abovethe mine.

[Pg 25]The mushroom anchor.—The 1,000-pound anchor is in shape a rightcylinder about 10 inches in height and 26 inches in diameter, slightlydished on the bottom to increase the holding power in mud. For a rockbottom six projecting toes increase the holding power; correspondingdepressions on the top permit piling when in store. The heavy anchors,2,000 and 3,000 pounds, are of the same form. The cylindrical form isadopted to facilitate handling, since in that shape the anchor may berolled readily on its edge.

The absolute stress of the mine and its moorings upon a mushroom anchorof this kind is easily computed, being the square root of the sumof the squares of the buoyant effort and of the horizontal pressureexerted by the current. The latter, in pounds per square foot ofexposed cross section, may be estimated at one-half the square of thevelocity of the current in feet per second. A coefficient of safetyshould cover the jerking effect of the waves and the shocks of friendlyvessels. It will, of course, vary with the locality and with theabsolute weight of the anchor, but in general a value from 3 to 5 isconsidered sufficient.

The holding power of such an anchor varies greatly with the nature ofthe bottom. If this be hard, the dead weight alone must be dependedupon; if soft, at least double power may be anticipated. In swift waterthe buoyant mine can be better held in position by two anchors chainedtogether.

The shackles.—The wire mooring rope is attached to the anchorand to the case by shackles, of which there are two sizes. The anchorshackle consists of a wrought iron strap with two eyes bent intothe usual curved form and offering a thickness of 1½ inches at thebottom, where the wear and sand cutting is greatest, and of a 1½-inchwrought iron bolt fitted flush with the outside of the straps. The boltis held in position by a split key, which, after insertion througha small hole in the bolt and one of the eyes (in the old model), isopened so that it can not work loose.

The mine shackle is lighter, being 1 inch thick at the bottom, witha 1-inch bolt; otherwise it is identical in pattern with the anchorshackle.

Sister hooks.—They are used to connect the bail of the mushroomanchor to the anchor shackle. They are of drop-forged steel of hightensile strength and weigh about 7 pounds per pair.[Pg 26]

The automatic anchor, Artillery type, 1910 (see figs. 10a and b).—This is a deviceintended for use with buoyant mines, and by means of which such minesmay be anchored in any depth of water, with any desired depth ofsubmergence given automatically.

The anchor is bell-shaped, 28 inches in diameter at the bottom, 28½inches high over all, and composed of the following parts: Body, cover,reel, journal-box caps, ratchet, pawl, pawl spring, distance rope,distance weight, brakes, bails, necessary bolts, wrenches, and crankhandles.

The pawl is drawn away from the ratchet by a weight suspended a certaindistance below the anchor. This is called the distance weight, andthe submergence is regulated by the distance this weight is from theanchor. In falling through the water the mooring rope will unreel andthe mine will remain on the surface, but when the distance weightreaches the bottom the pawl spring forces the pawl into the teethof the ratchet, and as the latter is attached to the reel shaft, itprevents the reel from turning and hence unreeling.

These anchors weigh approximately 1,500 pounds, including the 200-pounddistance weight.

In order to control the speed of revolution of the reel, the frictionbrakes must be adjusted properly. To do this, a pull is put on themooring rope with a spring balance rigged to show the amount of pull;the pull for a particular size of case is determined by experiment.For a No. 40 mine case the adjusting screws of the brake shoes areregulated so that the reel will revolve slowly when a pull of 300pounds is registered.

The pawl spring is 9½ inches long and of such strength that a pull of36 pounds will extend the spring 1½ inches. The pawl spring bolt is ofsuch length that the pawl spring will be just at the point of tensionwhen the top of the pawl spring bolt is flush with the top of thepawl spring-bolt nut and the pawl fully seated in the ratchet.

When the tidal currents are such as to require a heavier anchor tohold the mine than the 1,500-pound automatic anchor, the followingcombination anchor will be used: Attach a mushroom anchor by means ofa mooring rope (about 8 feet long) and clips to the bail in the bottomof the automatic anchor. If necessary, two mushroom anchors may befastened together by bolts and these attached to the automatic anchoras stated above.

[Pg 27]A 3,000-pound automatic anchor, similar to the 1,500-pound automaticanchor, is supplied for some localities.

The mooring sockets.—To connect the wire mooring rope to theshackles at the mine and the anchor, a closed socket is attached ateach end. The eye of the socket has a clear opening, 1³/₁₀ inches,designed to receive the bolt of the shackle. The end of the rope ispassed into the socket, spread out, and secured by pouring in a meltedsocket alloy.

A substitute method for connecting the wire mooring rope to theshackles is to bend the ends of the mooring rope by means of a smallvise around a galvanized iron thimble and fasten the end by two boltedclips.

Wire mooring rope.—This is the highest grade of ¾-inchgalvanized-steel wire rope, consisting of 6 compound strands, eachmade of 19 wires, the whole laid around a steel center. Its breakingstrength when new is about 18 tons. Its weight per running foot,submerged, is about eight-tenths of a pound. It is used for mooringmines to mushroom anchors.

Marline-covered wire mooring rope.—For mooring mines to theautomatic anchors and for raising rope marline-covered wire rope isused. This rope consists of five outer strands wound around a centralhemp core. Each of the outer strands consists of a small twisted wirerope wound around with four strands of marline. One end of the ropeis prepared for attachment to the mine by passing it over a thimbleand fastening it to the standing part by means of two clips. A shacklejoins the thimble and the bail of the mine. The other end of therope is made secure to the reel of the anchor. The breaking strengthof ½-inch marline-covered rope is 17,000 pounds, that of ⅝-inchmarline-covered rope is 27,000 pounds. The weight per running foot ofthe ½-inch rope is 0.5 pound, that of the ⅝-inch rope is 0.8 pound. Theweight of this rope submerged is about 60 per cent of its weight in air.[Pg 28]

About 155 feet of the ½-inch and 85 feet of the ⅝-inch marline-coveredrope can conveniently be wound on the 6-inch reel of the 1,500-poundautomatic anchor.

Marline-covered wire distance weight rope.—For attachingdistance weights to the automatic anchor ¼-inch marline-coveredwire rope is used. This rope is identical in pattern with themarline-covered wire mooring rope.

The distribution box, 19-conductor.—This is a circular,cast-iron, disk-shaped box which receives the end of the multiplecable, in which taped joints are made between the separate conductorsof this cable and the single-conductor mine cables, and from whichthese mine cables radiate. It is about 27 inches in diameter and weighsabout 300 pounds. It consists of two parts, a bowl-shaped bottom 6inches deep inside and a slightly curved lid. The latter has an ironring in its center by which the box is raised and lowered.

Eight pins, fastened to the bottom, fit in corresponding holes in theedges of the lid and are slotted for keys by which the two parts arefastened together.

The vertical edge of the bottom is cut with 20 slots, each about 2½inches deep. One of these is larger than the others and receives themultiple cable; the others are for the single conductor cables. Whenin use these slots are numbered clockwise from the multiple-conductorslot, looking down into the box. The lid has corresponding projectionsor lugs which enter these slots, and which, in position, fit snuglyagainst the cable ends. The cables are held from being pulled out byTurk’s-heads worked upon them.

To prevent the cable ends from accidentally slipping out of the slotswhile joints are being made between them before the lid is put on,the multiple cable is secured by a bolted collar on the inside of thebox, the single-conductor cables by clipping their Turk’s-heads underclaw-like radial projections cast upon the inside rim between the slots.

The distribution box, 7-conductor.—This box is used withmultiple cable, 7-conductor. It consists of two circular plates ofcast-iron 21 inches in diameter and three-fourths of an inch thickunited by four 1-inch bolts, which are placed in rounded projections[Pg 29]forming the angles of a square. The cables are separately clamped, thetop plate overlapping the clamp straps. The multiple cable enters onone side; three single-conductor cables enter on the opposite side, andtwo on each of the intermediate sides. The top plate is provided with alowering ring.

The junction boxes.—These boxes, in different sizes, are usedin splicing multiple and single-conductor cables; they consist of tworectangular plates of iron or steel united by four ½-inch bolts at thecorners. The plates are hollowed in the middle to form a chamber toreceive the Turk’s-heads and the joints connecting the conductors. Theends of the plates are curved to admit the cable ends. The Turk’s-headsare clamped to the lower plate by straps and screw bolts, the cavity ofthe upper plate covering them when bolted in position. Each cable endis thus made fast before the box is closed.

The distribution box buoy.—This buoy is used to mark theposition of the distribution box during the planting of mines andsubsequently, in practice and in service, until such time as the minecommander desires to remove it. It may be either a can or a keg buoy—abeer keg of one-half barrel capacity is well suited for this purpose.

The mine buoy.—This buoy is used to mark the position of themine when planted. It may be a small can buoy, preferably cork filled,or a piece of wood with a hole bored through it. The size of the buoyis determined by the swiftness of the current. It is attached to themaneuvering ring of the buoyant mine by 60 feet of ½-inch rope.

The measuring reel and frame.—The frame consists of twolongitudinal pieces, 3 by 4 by 66 inches, placed 17 inches apart,center to center. At 11½ inches from each end two cross pieces, 3 by 4by 20 inches in length, are fastened to the longitudinal pieces withthrough bolts. At the center point of these cross pieces are placedstandards, 3 by 4 by 16¾ inches, which have journals for the axle ofthe reel, counter-sunk in their upper ends. Two iron braces, one oneach side, hold each standard firmly in a vertical position. An ironclamp is also attached to the upper ends of the standards, by means of[Pg 30]which the axle is prevented from jumping out of the journals. Distancefrom center to center of standards is 43 inches.

The iron axle of the reel is 1½-inch round iron, 54 inches in length.At each end of the axle a screw thread is cut for the nut which holdsthe crank in place. Inside the screw thread the axle is squared toreceive the socket of the crank. Two collars prevent the woodenreel from binding on either standard. The cranks are of the usualdesign. The drum of the reel is 8½ inches in diameter; heads are 2½inches thick, made in two layers, cross-grained, and are 24 inchesin diameter; length of drum over all is 36 inches. Iron plates arefastened in the center of each head, through which the axle passes. Thereel is prevented from turning on the axle by keys.

Three ¾-inch rods pass through the iron plates and drum and bind theseparts firmly together.

At 6 inches from the ends of the longitudinal pieces a hole is bored toreceive a lag screw, ½ inch by 6 inches, by means of which the wholeapparatus can be firmly fastened to the deck.

The brake is a piece of 3 by 3 by 36 inch hardwood, used as a lever tobring pressure on the drumhead. There is one for each side, and, whennot in use, each rests on one of the longitudinals, being held in placeat one end by two staples and at the other end by a bolt and pin.

Near the drum on one head is a hole through which the inner end of themeasuring line can be passed and stapled to the outside of the head.

The cable-reel frame.—The frame is made in two parts which,when in use, are held in proper relative positions by means of two ironties provided with turnbuckles at their centers. The ends of these tiesare bent over at right angles and fit in sockets in the two end parts.

Each end part consists of a standard having an iron head through whichworks a screw turned by a small lever, the upper end carrying a journalin which the end of the reel axle rests. The lower end of the standardrests on a horizontal piece and has a diagonal brace on each side, theouter ends of these braces being dovetailed into the longitudinal pieceand the inner ends into the standard near the top. Dovetailed into thelongitudinal piece at its middle point is a piece extending out atright angles, bottom flush with bottom of the longitudinal. A diagonalbrace similarly fastened prevents any outward movement of the standard.The whole is held firmly together by bolts and lag screws.

[Pg 31]Lag screws are also provided, by means of which the ends of the framescan be fastened to the deck of the vessel if desired.

The reel axle is 2½ by 2½ inch squared iron, rounded at the ends for 6inches to fit the journals of the frame. A disk secured by a set-screwat one end of the axle and the friction brake wheel at the other endhold the axle in position with respect to the reel.

The brake wheel is 18 inches in diameter. The friction band is 1½inches by ⅛ inch, and is fastened at one end to one of the standards ofthe frame. The other end is attached to a lever whose fulcrum is alsoattached to the same standard.

Boat telephones.—The different models in use are as follows:

(a) Model 1904.—The system consists of two telephonehand sets, a buzzer, and a battery of dry cells of about 8 volts, allconnected in series by means of cable and earth connections.

In operating the telephones a call is made by pressing the button, andwhen talking the lever is held down.

(b) Model 1906.—The system consists of two telephonehand sets, a reactance coil, and a source of energy that will furnishabout 15 volts, dry cells preferred, connected as shown in figure 11.The terminals do not have to be poled, as the receiver is not in theprimary circuit and can not be demagnetized.

To regulate the buzzer, remove the cap in the base and with a smallscrew driver loosen the lock nut on the center screw (a small portionof a turn is all that is necessary). With a smaller screw driver thescrew may be adjusted to increase or decrease the rate of vibration,increasing or decreasing the sound. Then tighten the lock nut. In casethe contact is dirty the entire buzzer and condenser may be removed by[Pg 32]disconnecting the cord and removing the screw on the back of thetelephone just below the call button. As the contacts are aluminum,this will seldom have to be done.

(c) Model 1909.—The system consists of two telephonehand sets, an apparatus box, and a battery of from 7 to 10 volts, allconnected as shown in figure 12. The talking andringing circuits are normally open at the talking and ringing buttons,respectively.

Apparatus box.—Seven dry cells in series should be connected tothe posts of the apparatus box marked “+” and “-,” and the post marked“G” connected to a ground plate.

Shore hand set.—The blue cord of the shore hand set should beconnected to the ground plate. Either of the red cords of the shorehand set should be connected to the post in the apparatus box marked“L” and the other to the conductor in the cable that is to be used fortelephoning purposes.

Boat hand set.—The blue cord of the boat hand set should beconnected to the ground plate and one of the red cords to the conductorin the cable to which the hand set on the shore is connected. The otherred cord is free.

Signaling.—From figure 12 it will beseen that in either hand set, when neither the ringing nor the talkingswitch is closed, a condenser within the hand set is in series with thetransmitter and the receiver, so that the practical effect is to permitan alternating or variable current to pass through the transmitter andthe receiver, but to prevent a direct or continuous current from so doing.

By pressing the ringing key of either hand set the circuit in thathand set is closed through the 1,000 ohms resistance and the receiverto ground. Thus, when the ringing key of the boat hand set is pressed,this allows the direct current from the battery to pass (see fig. 12)through f, e, d, c, “B,” b, a, line, the ringing key, 1,000-ohmresistance, and receiver of the boat hand set, to ground, and backthrough o and p to battery. Similarly, a circuit through the battery,f, “A,” and a, is made, thus placing relays “A” and “B” in parallel.The relay “B” operates, but relay “A,” being less sensitive than “B,”does not operate. Relay “B” closes the circuit at l, and thus completesthe circuit from battery through f, e, d, c, k, l, “C,” o, p, backto battery. This causes relay “C” to operate and to complete a localcircuit from battery through f, e, d, k, m, s, primary, t, vibrator,p, back to battery, causing the vibrator to vibrate and inducing inthe secondary winding of the induction coil an alternating current,which passes through the 1 M. F. and 2 M. F. condensers, through thehand sets in parallel, and by alternately increasing and decreasing theattraction of the receiver magnets for their diaphragms produces a loudhumming sound in each receiver.

Similarly the shore station may call the boat station.

[Pg 33]Talking.—When the ringing key is released and the talking keyis depressed the 1,000-ohm resistance is cut out and the condenser inthe hand set is short circuited. The current is then sufficient tooperate relay “A,” and this relay in operating allows the other relaysto resume their normal positions.

When the variations in the pressure upon the transmitter diaphragmin either hand set varies the resistance of the corresponding branchcircuit a slight variation in the current from the battery is produced.The internal resistance of the battery is sufficient to produce aslight variation in its terminal voltage. The resulting variations inthe line voltage, and hence in the drop across the receivers, producethe usual vibrations in the receiver diaphragms. These variations alsoproduce slight variations in the current through the primary windingof the induction coil, resulting in greater variations across theterminals of the secondary winding. Since the secondary winding isin series with the battery, the practical effect is to amplify thevariations in the line voltage, and hence in the talking currents.

Successful working of the relays is obtained only by a carefuladjustment of the screws which regulate the throw of the armatures. Therelay “A” is located in front of the “+” battery post, the relay “C” infront of the “G” post.

In addition to the above matériel there are necessary for the minesystem certain electrical instruments, as well as tools, appliances,and supplies requiring no special description, which are enumerated inthe supply list. (Appendix 8.)

Figures 17a and 17b,at the end of the book, show the construction of an improvised mine target.

Making a telegraph joint.—The insulation is removed from theends for 1½ inches and the wires brightened. The ends to be joined areplaced across each other about one-third distance from the insulation,making an angle of about 45° with each other. The wires are graspedfirmly at the junction and each free end wound tightly around the otherwire for four turns; the winding should be in opposite directions. Theends of the wires are trimmed down so they will be smooth and presentno sharp points.

When wires are joined with brass jointers three-fourths inch of eachwire is bared and the wires are inserted in the jointer; each end iscrimped with pliers in the direction of the longer axis; the rest ofthe jointer is crimped and the ends or sharp points rounded off. Whenbrass jointers are used care should be exercised not to crimp themtoo hard, as the wires may be partly cut through and finally broken.Special care must be used with the fuse leads, as the secondary circuitof the mine transformer can not be tested after the compound plug isassembled.

Insulating a joint.—A piece of rubber tape about 2 inches longis used, with ends cut diagonally. The tape is stretched, and startingat a point about three-fourths inch back on the insulation, with thelong edge of the tape on the inside, it is wound around the joint undertension, each turn covering the previous turn about one-third. Thewrapping is continued until the same amount of insulation is covered oneach side, when the wrapping is worked backward over the joint and theend is secured by pressing it firmly a short time or placing a drop ofcement under it.[Pg 35]

Making a water-tight joint.—The two ends of wire are scrapedclean for about three-fourths of an inch and joined by a brass jointer,which is then crimped. The insulation is scraped clean about 2 incheson each side of the jointer and covered with rubber cement. (Cementis not absolutely essential.) Two strips of rubber tape are cut about6 inches long, with diagonal ends, and stretched. Beginning about1½ inches along the insulation, the tape, with the long edge on theinside, is wrapped firmly and tightly until about one-fourth of an inchof the insulation on the other side is covered; it is wound back andforth over the joint so as to taper toward the ends. The other pieceof tape is used, beginning at the other end and wrapping as before.The finished insulation should be thick at the middle and taper towardthe ends. It should be firm and tight. The insulation is covered withtin foil, wrapped with protective tape, and vulcanized for about 30seconds. The protective tape and tin foil are then removed, the jointinspected, and new protective tape wrapped on, using two pieces,starting at opposite ends and finally ending each beyond the center.

Making a Turk’s-head.—The cable is trimmed square and awrapping of four or five turns of marline is made about 15 inches fromthe end. The collar, flat side first, is slipped on until it rests onthe marline; the iron wires are bent back regularly over the collar.The jute wrapping is unwound to the collar and trimmed, and all theiron wires are cut with the pliers, removing all but 4 inches and 6inches from alternate strands; the iron wires are bent separately tofit the collar closely (making two right angles with the pliers), andthe ends arranged smoothly along the cable; the end of a piece ofmarline is engaged under one of the wires near the collar and wrappedregularly and closely around the cable, and the free end of marlinesecured with two half hitches. About 15 feet of marline are requiredfor single conductor cable; 24 feet for multiple cable.

Testing fuses.—The following apparatus is used for testing in[Pg 36]the loading room: A double-pole double-throw switch, a 150-voltvoltmeter, and sufficient dry cells to give a full throw when usingthe lower scale of the voltmeter. The apparatus is connected up on thetesting table so as to make resistance measurements by the voltmetermethod. To test fuses, leads are carried from the switch to an iron orother suitable receptacle outside of the building and the fuse leadsjoined thereto. A full deflection should be obtained when the circuitis closed through the fuses.

Preparing a compound plug for service.—The transformer to beused is first tested for a good circuit between the red wires, a poorcircuit between the ends of the black wire, a good circuit between theblack or primary lead and the reactance terminal, no circuit betweenthe red and black wires, and no circuit between any wire and the case.The resistance of the circuits is determined by the voltmeter method.The upper end of the black wire (see fig. 8)is prepared for use by baring the wire for about one-half inch andsecuring it to the binding post in the neck of the transformer. Theball seat is screwed home. The spring plate, distance ring, and ballare placed in the circuit-closer cap, which is held inverted and thetransformer screwed into it, the threads being coated with ruberine.

(a) Old model, brass fuse can.—Starting with thecompound plug dismantled.

A piece of loading wire is cut about 3 feet long and the ends bared.One end is joined by a telegraph joint to the primary terminal of thetransformer and the joint is taped. This wire and the two secondarywires are drawn through the fuse can, which is screwed on thetransformer, the threads of the latter having first been coated withruberine.

Two mine service fuses, which have been tested for continuity ofcircuit, are connected in multiple across the secondary (red) terminalsand the joints taped.

The can is held vertically and the explosive, if trotol, poured inup to the screw threads for the fuse can cap; if dynamite, inclosed in acloth bag and placed in the can. The fuses are embedded in the explosive.[Pg 37]

The loading wire is drawn through a lead washer and the fuse can cap;the latter, its threads having been coated with ruberine, is screwedinto place.

A rubber packing is pushed over the loading wire into the stuffingbox in the fuse can cap, a brass gland is threaded down so that it isclose against the rubber packing, and the follower is screwed home withmoderate pressure. The lower tube is screwed into place, compressinga lead washer between it and the fuse can cap. The threads of thefollower and lower tube are coated with ruberine.

The loading wire is drawn through a lead washer and the hole in theplug proper, and the latter screwed hard against the lower tube.

A rubber packing and a brass gland are placed upon the loading wire andforced into their seat in the plug proper by means of the follower, thethreads of which have been coated with ruberine.

(b) Rubber fuse can.—Starting with the compound plugdismantled.

Two mine service fuses, which have been tested for continuity ofcircuit, are cut with 9-inch leads, wires bared for about 1 inch andconnected in multiple. A piece of loading wire is cut about 3 feet longand the ends bared for telegraph joints. It is threaded through a holein a cake of dry guncotton. The two fuses are inserted by pushingeach separately into the same hole and the loading wire drawn up untilit is the same length above the cake as the fuse leads.

Three other primer cakes are threaded on the wire; two above the fuses,and one below. This arrangement will leave the fuses in the third cake.The cakes are held in one hand with the fuse leads upright, and thefuse can slipped over the cakes, being careful to thread the fuse leadsand loading wire through the opening.

The screw threads of the fuse can cap are covered with ruberine and itis screwed firmly into place onto the fuse can. The stuffing box of thecap is assembled.

The plug proper is held upright in a vise. The fuse can, the threads of[Pg 38]the cap having been coated with ruberine, is screwed home and securedby its set-screw. The loading wire must be pulled through the openingin the plug proper with extreme care. It must not be injured in placingthe fuse can in position and in screwing it home. The transformer leadsare cut about 6 inches long, and the ends bared for 1 inch. The brasscollar is screwed on the transformer; a little ruberine on the screwthreads facilitates the operation. The connecting collar is slippedover the fuse leads and loading wire and allowed to rest on the fusecan. The transformer is supported by allowing two of the connectingbolts to slip into the holes in the collar; telegraph joints or brassjointers may be used between the secondary leads and the fuses andbetween the primary lead and the loading wire. The joints are woundwith rubber tape, care being taken that there are no sharp ends to cutthrough the tape.

The transformer is raised vertically above the fuse can until the leadwires are extended. It is lowered and at the same time the leads arecoiled in the base of the transformer. As the transformer and collarapproach their position on the connecting bolts, the connecting collaris screwed on the transformer, the threads of the transformer havingbeen covered with ruberine. The connecting collar will take care ofthe remainder of the leads and joints. The set-screw in the connectingcollar is screwed home; the brass collar is placed on the connectingbolts and secured in position by the nuts and cotter pins.

The lips of the fuse can and connecting collar are covered with athin covering of rubber cement. A piece of rubber tape is cut about18 inches long and laid around this opening without stretching. Apiece of protective tape is cut about 18 inches long and laid over therubber tape with considerable stress. This forces the soft tape overthe lips on the connecting collar and the fuse can and makes a tightbut flexible joint. The stuffing box in the plug proper is prepared asunder (a).

Great care must be taken not to injure the insulation of the loadingwire in tightening up the follower in the stuffing box of the fuse canor of the plug proper.[Pg 39]

(c) Trotol fuse can.—Starting with the compound plugdismantled.

Two mine service fuses, which have been tested for continuity ofcircuit, are cut with 12-inch leads, the wires bared for 1 inch andconnected in multiple. A piece of loading wire is cut about 3 feet longand the ends bared for telegraph joints. The loading wire is threadedthrough the fuse can and cap. The threads of the fuse can are coveredwith ruberine. The can is screwed into the cap. The threads of theconnecting collar are coated with ruberine and the collar is screweddown entirely. The loading wire should project about 4 inches above theconnecting collar. The stuffing box of the cap is prepared. The plugproper is held upright in a vise. The fuse can cap, its threads havingbeen coated with ruberine, is screwed firmly into the plug proper bymeans of a spanner wrench. The loading wire must be pulled through theopening in the plug proper with extreme care. It must not be injured inplacing the fuse can in position and screwing it home.

The fuses are inserted in the fuse can, which is filled with trotolto the top of the connecting collar. The transformer leads are cut 4inches long and the ends bared for 1 inch. The threads of the brasscollar are covered with ruberine. It is screwed on the transformer.The latter is raised vertically above the fuse can and lowered on theconnecting bolts.

Telegraph joints are made between the secondary leads and the fusesand the primary lead and the loading wire. The joints are wound withrubber tape, care being taken that no sharp ends cut through the tape.The leads and joints are coiled in the base of the transformer. Theconnecting collar, its threads having been covered with ruberine,is screwed upon the transformer against the brass collar. Thebolt-securing nuts and cotter pins are placed in position. The stuffingbox in the plug proper is assembled as under (a).

The actual resistance of the assembled plug in the vertical and thehorizontal positions is determined by testing with a voltmeter.

[Pg 40]

In service, after the loaded plug tests out satisfactorily, all setscrews are set up.

When compound plugs are prepared for drill or for instruction purposesthe use of ruberine or other waterproofing material on the screwthreads is omitted; care must be taken that the transformer leads arenot needlessly shortened.

Loading a mine.—The mine case is carried from the storeroomto the loading room and placed on a loading skid or other receptaclewith the loading hole up. The plug is removed and the screw threadsare thoroughly cleaned. The explosive detail brings in a box ofexplosive from the explosive house and inserts a loading funnel intothe loading hole. The charge for a 32-inch mine case is 100 poundsof explosive. For the larger cases, the charge should be the maximumthat the conditions warrant; it is specified at present as 200 pounds,though larger charges are desirable if enough explosive can be obtainedand the excess buoyancy of the case will warrant the use of more than200 pounds. The cartridges of dynamite, the trotol, or the blocks ofguncotton are inserted by hand and so placed in the mine case thatthere will be ample room for inserting the compound plug. Only one boxof explosive for each mine being loaded is brought into the loadingroom at one time. After the proper amount of explosive has been placedin the mine case the screw threads are thoroughly cleaned with buttonbrushes and then coated with ruberine or other material to preventaccess of water. The compound plug, with its screw threads similarlycoated, is screwed home with the socket wrench, a lead washer beingused between the plug and mine case. A bar put through holes in thesides of the skids and through the maneuvering ring will prevent thecase from falling over and from turning while the compound plug isbeing screwed home.

In order to insure setting the compound plug tight, it is advisable totap the end of the lever of the socket wrench a few times with a largemallet or a large wooden bar. The mine cap is bolted on and the mineput in a tank for test. If time admits, it may remain in the water 24[Pg 41]hours. It should show practically the same resistance as the compoundplug. If this test be made, the loading wire must be long enough forthis purpose.

Upon completion of this test the mine is taken from the tank, theloading wire pushed inside the cap to avoid injury in handling, and theloaded mine taken to the planting wharf.

The precautions to be observed in handling explosives and loading minesare given in Appendix 1.

(Note.—Theoperations in Chapters IV and V are described in what is thought to bethe logical order, but circ*mstances may alter their sequence, and, infact, several of the steps may be carried on simultaneously.)

For the work on the water there will be needed five boats, viz., a mineplanter or suitably fitted-up heavy tug, a small tug or heavy launchcalled the distribution box boat, and three launches or yawls. Thecapacity of the planter is such that a group of 19 mines can be handledat one time.

The instructions to be observed by the master of a mine planter inmarking out a mine field and in planting mines are to be found inAppendix No. 6.

Determining location for distribution box.—From an examinationof the chart, or of the approved scheme for mining, the locations ofthe lines and groups of mines are determined. A distribution box is tobe placed about 350 feet in rear of the center of each group of mines.The locations for the distribution boxes are marked on the plottingboard and their azimuths from each of the ends of the horizontal baseor their azimuth and range from the vertical base station are determined.

Marking location of distribution box.—An anchor with buoyattached is placed upon the deck of a small tug and carried out to oneof the selected spots. By a system of signals the boat is directed tothe location determined and there the anchor is thrown overboard. Thelocations for the other distribution boxes are marked in a like manner.

Laying multiple cable.—The cable-reel is placed upon the[Pg 43]forward deck of the planter and raised on the jacks. The planter thenproceeds as near the mining casemate as the depth of water permits, andone end of the cable is passed ashore, either by a launch, by yawls,or by any other suitable method. In case the planter can not approachnearer the shore than 100 yards it will be necessary to coil more thanenough cable to reach the shore in a figure of eight in a yawl, whichis then towed toward the desired point on shore, the men aboard theyawl paying out the cable as it proceeds. This end is drawn in throughthe conduit or gallery to the casemate or terminal hut. It may besecured by taking a telegraph hitch around it with a chain and spikingthe chain to some heavy timbers or fastening it to some holdfast. Whencable ends have already been laid they will be picked up and joined tothe multiple cable for the groups.

The shore end having been secured, the planter moves out to theposition of the distribution box, unreeling the cable as it goes.If the water be very deep, a friction brake must be extemporized toprevent the reel from overrunning. (While the planter is laying thecable, the casemate party tags and attaches the shore end as explainedlater.) To prevent kinks as far as possible cable should be laid withas much tension as practicable.

If the cable is not long enough, a second one must be joined to it.This is preferably done by passing the ends to a small boat. Thejunction is made, either using a junction box with Turk’s-heads andtaped joints, or opening back the armor for about 5 feet from the ends,making taped joints, protecting them with tape, and then rewrapping thearmor and seizing the ends with wire. Care must be taken to join theproper conductors of the two ends.

In the meantime the distribution box boat with a detachment of onenoncommissioned officer and five men takes the distribution box andmoves out to the spot marked by the buoy. It picks up the buoy andmakes fast to the anchor line.

The planter continues laying the multiple cable until it reaches thedistribution box boat. The multiple cable is then cut and the endpassed to the distribution box boat, usually by a heaving line. The[Pg 44]cable is lashed to the boat; a Turk’s-head is worked upon the end andthen secured in the distribution box. As a precautionary measure forthe recovery of the distribution box, should it be lost overboardduring mine planting, it is well to have the multiple cable buoyedabout 100 yards in rear of the distribution box.

In case it may be desired not to use the distribution box at once, theseparate conductors of the multiple cable should be tagged, tested,and insulated. The cable should be buoyed and dropped overboard to berecovered subsequently.

Identifying, tagging, and testing the conductors of the multiplecable.—Tagging.—In the casemate the conductors are separated,carefully identified, tagged, and attached to the corresponding terminalof the terminal bar on the operating board. The mine switch for No.19 is opened and the telephone terminal attached to its stud so asto use No. 19 for communicating with the distribution box boat. Theends in the distribution box boat are separated, one terminal of aboat telephone is attached to No. 19, and the other earthed either byattaching to the cable armor or to an earth plate hanging overboard inthe water. Communication is thus established with the operator in thecasemate. Nos. 1, 13, and 19 are picked out easily; the remaining onesare tagged in contraclockwise direction.

Verifying the tagging.—The casemate is then notified that theboat party is ready to check the tagging. This is done as follows:The power switches on the operating board are all closed, except 19,and direct current put on the cable by closing switch No. 3 up. Thecasemate operator then directs the boat party to earth in regularsuccession the various conductors. This is done most quickly bytouching the conductor to the cable armor. The corresponding automaticswitch on the operating board should drop. Any errors in taggingdetected by this test should be corrected at once. This test alsochecks the continuity of circuit of each conductor.

Insulation test.—The operator then directs the boat party toprepare the cable end for insulation test. This is done by separatingthe conductors, holding them in the air, and drying them if necessary.[Pg 45]

When prepared, word is sent to the casemate operator, who tests asfollows: He closes switch No. 7 up. This throws D. C. power on themil-ammeter plug of the operating board and introduces in the circuitthe mil-ammeter and its protective lamp. The green lamp is thenunscrewed and the mil-ammeter plug used on the D. C. jaw.

If there be no leak in the multiple cable, since the ends at thedistribution box boat are held in the air, there will be no appreciablereading of the mil-ammeter.

If there be a leak, this fact will be revealed by a reading on themil-ammeter. To discover the particular conductor or conductors onwhich this leak exists, each power switch is opened in succession andthe mil-ammeter plug inserted on the jaw of the power switch.

No. 19 is now tested in the same way by first shifting both telephonesto No. 1, the boat end being held in the air. The operator reports theresult of the test.

Upon completion of these tests the power is turned off. Post powershould not be used for testing, because the negative side of the postpower may be grounded.

Marking out the mine field.—In using automatic anchors it isnot necessary to mark the mine field; but in using mushroom anchors itis generally done. The material required consists of 1 measuring linewith reel and frame, 5 anchors, 5 keg buoys, and 5 raising ropes.

A buoyed anchor is dropped about 350 feet in front of thedistribution box buoy. This marks the position of mine No. 10 and ofthe center of the group.

This marking buoy is picked up by a launch which makes fast to theanchor rope. The planter now passes to the launch one end of ameasuring line, which has marks at 280, 300, 350, 580, and 600 feet.These marks may be made by painting 3 feet of the measuring linesome distinctive color at the designated points. The planter movesout slowly along the line to be occupied by the mines, unreeling themeasuring line as it goes, and drops buoys at the 300 and 600 footmarks. It then returns and does the same for the other side of the[Pg 46]line. These five buoys mark the line to be occupied by the mines,indicate the positions of mines Nos. 4, 7, 10, 13, and 16, and inaddition cut up the distance into 300-foot lengths, which enable theplanter to plant mines at a close approximation to 100 feet apart.

Taking soundings on line of mines.—When automatic anchors areused, such information as may be required about depth of water mayusually be obtained from charts. This may not be sufficiently accuratefor planting with ordinary anchors. In the latter case soundings mustbe taken at the spots where the mines are to be planted.

These soundings are made from the launches. The launches take ameasuring line marked at every 100 feet, stretch it between the plantedbuoys, and take the soundings at every 100-foot point. The soundingsare recorded in a blank book showing the number of the correspondingmine and state of the tide. It may be found more satisfactory to holdone end of the measuring line at the buoy and circle across the line ofmines with the launch, getting the sounding at the point of crossing.

Preparing mooring ropes.—The mooring ropes are cut off withsquare ends, and the ends passed through the holes in the mooringsockets. The strands and wires are untwisted and spread out for alength equal to the length of the socket hole. The rope is pulled backuntil the ends are about flush with the top ends of the hole; a pieceof marline is tied about the rope below the socket. If necessary tohold the socket, a piece of burlap may be wrapped around below thesocket, and a fold allowed to fall over the hand. Generally, meanscan be found to set the socket upright while pouring full of alloy.The alloy consists of 9 parts of lead and 1 part of antimony meltedtogether. A melting pot heated by a plumber’s furnace, or preferablya Khotal lamp, is used for this purpose. Great care must be taken tosee that there is no oil or water on the socket or mooring rope beforepouring the alloy.

The length of the mooring rope for buoyant mines No. 32 equals the[Pg 47]depth at low tide, less 15 feet. This allows 5 feet for the lengthof the mine, anchor, and shackles, and 10 feet for submergence. Whenthimbles and clips are used the mooring rope is cut 3 feet longer andis bent back a foot and a half at each end for the thimbles and clips.

For the larger mine cases, an additional allowance must be made for thelength of the cylindrical part of the case.

Each mooring rope is carefully tagged at each end with the number ofthe corresponding mine.

Note.—Theinstructions to be observed by the master of a mine planter in markingout a mine field and in planting mines are to be found inAppendix No. 6.

The planter detail.—This consists of the chief planter and 3noncommissioned officers and 16 privates, distributed in three details,as follows: One noncommissioned officer and six privates on each sideof the planter and one noncommissioned officer and four privates aft.

Tools and supplies.—The tools and supplies to be taken aboardfor the work described are:

• On the planter.
• Alcohol.
• Anchors.
• Axe.
• Boat hooks.
• Buoy, key.
• Buoys, mine.
• Cable cutter.
• Cables, multiple.
• Cables, single conductor.
• Cable tags.
• Clips, cable.
• Cotter pins.
• Crank handle for automatic anchor.
• Dry cells.
• Grappling hooks.
• Hammers.
• Heaving lines.
• Kerosene.
• Knives, submarine mine.
• Lamps, alcohol (2).
• Life buoys (3).
• Marline.
• Marlinespikes.
• Matches.
• Megaphone.
• Mines.
• Monkey wrenches.
• Nuts.
• Ropes, mooring.
• Ropes, raising.
• Shackles, anchor.
• Shackles, mine.
• Shoes, mine-cap.
• Sister hooks.
• Spring balance.
• Stamping outfit.
• Tools and materials necessary to make
• Turk’s-heads and joints.
• Voltmeter.
• Washers.
• Waste.
• Wire, soft-drawn copper.
• Wrench, socket, for automatic anchor.

• On distribution box boat.
• Alcohol.
• Anchors, boat (2).
• Axe.
• Boat hook.
• Boat telephone with connectors and earth plate.
• Breaker of drinking water.
• Buoy.
• Cable tags.
• Compass, boat.
• Distribution box.
• Flags, boat (2).
• Gasoline (tankful).
• Green light.
• Hammers.
• Heaving lines.
• Kerosene.
• Knives, submarine mine.
• Lamps, alcohol (2).
• Lashings.
• Life buoys (2).
• Life preservers, one for each man.
• Marline.
• Marlinespike.
• Matches.
• Megaphone.
• Monkey wrenches.
• Notebook and pencil.
• Red light.
• Rope, raising.
• Ropes, buoy (2).
• Shackles.
• Tools and materials to make
• Turk’s-heads and joints.
• Waste.
• White lights (2).

• In each yawl.
• Anchor, boat.
• Anchor line.
• Boat hook.
• Heaving line.
• Life buoy.
• Life preservers, 1 for each man.
• Marline.
• Megaphone.
• Oars and locks (7).
• Sounding line.

[Pg 49]Preparing mine cables.—A reel of single-conductor cable istaken from the tank and placed on a cable-reel frame. A piece 20 feetlong is cut off the end to eliminate the part which was above waterduring storage. The cable for the mines is now unreeled, cut to thefollowing lengths plus twice the approximate depth of the water,and each end carefully tagged with the number of the correspondingmine. A Turk’s-head is made on each end.

The mine cables are coiled in figure 8’s. In order to secure uniformityin the size of the coils, they may be coiled on a rack (improvisedat the post). This rack is made of one 12-foot length of 4 by 6-inchscantling, crossed at right angles by two 6-foot lengths (4 by 6 inch)placed 5 feet apart. Four 1-inch holes are bored through each of thetimbers about 2 feet from each of the crossings, and a 2-foot length ofgas pipe is inserted in each hole. These pipes make the form on whichthe coils are made.

A cable must be coiled for planting so that both ends are free, one tobe passed to the distribution box boat, the other to be carried forwardon the planter and attached to the mine. This is accomplished bystarting the coil about 135 feet from the mine-cap end, the approximatelength required to run forward when using a mine planter. The cableis coiled on the form, spreading out the laps at the center to reducethe height at that point, until the entire length is coiled. The outerloops and the center of the figure 8 coil are lashed, leaving the ends[Pg 50]sufficiently long to lash the part of the cable remaining uncoiled. Themine-cap end of the cable is then coiled on top of the coil and lashedwith the ends of the rope.

Single-conductor cables when coiled should be tested for continuity ofcircuit and grounds before being placed aboard the planter.

For continuity of circuit the two ends of the cable are connected to abattery and voltmeter in series. If the cable has no break, the readingof the voltmeter should show approximately the same deflection as whenthe battery circuit and voltmeter alone are in circuit.

To test for a ground the cable is submerged in a testing tank, leavingboth ends out. It is advisable, when practicable, to extend a leadfrom one of the operating boards of the mining casemate to the cabletank. One end of the cable to be tested is connected to this lead andthe test made as prescribed for “insulation test” on page 44. Thecondition of a multiple-conductor cable can be quickly determined bythis arrangement. If the above method is not practicable, a dry-cellbattery with a mil-ammeter and protective lamp may be installed atthe cable tank; or, in place of the mil-ammeter and lamp, a voltmeterplaced in series with the battery and cable may be used, the resistancebeing obtained by the voltmeter method. One side of the battery shouldbe grounded by touching the cable armor or by using an earth plate. Inactual service, cable which tests under 1 megohm should not be used;for practice, cable under 10,000 ohms should not be used. If post poweris used as a source of energy for testing, the system should be freefrom grounds. Care should be taken to have the cable ends and batteryleads free from grounds and dry.

Cables are raised and lowered into the tank by means of a cableyoke, which consists of an 11-foot length of 4 by 6 inch scantling,with three hooks on the lower side and a ring on the upper side atthe center for hoisting. The lower hooks, which are secured to thescantling by a bolt and ring, hook into the lashing on the cable.Washers are placed under the bolt heads to prevent their slippingthrough the holes.[Pg 51]

Swinging or traveling cranes with triplex blocks are used for loweringand raising cable and yoke.

The coils of single-conductor cable are carried aboard the planter,to the aft deck, by the cable detail, or they may be lowered onto thedeck by means of the cable yoke and a derrick on the wharf. The cablefor mine No. 1 is placed on the starboard side of the aft deck and itsmine-cap end is carried forward on the cable racks close to the mines.The other cables, Nos. 2 to 9, inclusive, are placed in succession onthe starboard side in the same manner. The cables, Nos. 19 to 10 areplaced in succession on the port side, with No. 19 at the bottom. Thecoils on each side are placed on top of each other. The cable should beremoved from the racks when its corresponding mine is being preparedfor planting.

At the same time the other apparatus and appliances are carried aboardand placed forward, the proper supply on each side. The anchors areplaced as convenient to the forward davits as possible.

Finally, the loaded mines are put aboard. If they contain dynamite theyshould be protected from the direct rays of the sun by being coveredwith a paulin.

Preparing mines for planting.—The detail on each side of theplanter prepares a mine on its own side. The loading wire from themine is cut to the proper length, a water-tight joint is made with thesingle conductor of the corresponding cable, and the Turk’s-head isclamped in place, care being exercised that no part of the leading-inwire is caught under the clamp. The cable is lashed with soft-drawncopper wire or secured by clips to the bails just above the ring.

The proper mooring rope is now shackled at one end to an anchor, at theother end to the mine, and is lashed to the mine cable with soft-drawncopper wire at every 5 feet. If automatic anchors be used, the mooringrope is shackled to the mine after the anchor and mine are swungoutboard; the lashing of the cable to the mooring rope is omitted.

A rope for raising the mine is cut to the length of 80 feet plus thedepth of water. One end is attached to the anchor by an anchor knot or[Pg 52]bowline, the other to the mine cable by two half hitches and a seizingof soft-drawn copper wire. It should not be secured at other points.

The mine buoys have attached to them 60 feet of ½-inch rope, which ismarked at every 5 feet. The free end is slipped through the maneuveringring of the mine and tied to the buoy.

When planting mines for practice, marline may be used to seize theraising rope to the cable and to lash the cable to the bail and mooringrope.

A mousing must be put around the upper hook of the differential blockto prevent the block from jumping off the hook when the mine or anchoris tripped. The tripping hook of the differential block on the forwarddavit is attached to the anchor and it is hoisted and swung outboardclear of the rail. The mine is similarly slung from the after davit byits maneuvering ring or by a rope sling through the latter. Both mineand anchor are lowered as close to the water as conditions will permit.A heaving line is bent onto the free end of the mine cable, generallyby means of a clove hitch and two half hitches.

The aft detail now removes or cuts the rope lashings of the coil of thecorresponding mine cable. A detail sees that the cable and raising ropeare held on the gunwale ready for planting. These should not be allowedto trail in the water. A man stands near the mine davit ready to throwthe mine buoy clear of the planter when the mine is tripped. (Fig. 13shows the mine and anchor slung for planting and fig. 14shows the relative position of the various parts in the water. In these figuresthe cable should be shown as lashed to the mooring rope.)

The distribution box boat should precede the planter to the minefield. The distribution box buoy, to which the anchor rope is fastenedby a bowline, to the bight of which the raising rope is secured, istaken aboard at the bow, if the tide is coming in toward the box, andthe anchor rope is made fast. The distribution box is then raised byits raising rope and secured in the stern. The boat is thus anchoredfore-and- aft, perpendicular to the line of mines, with its bow pointedtoward the position of the center mine of the group. If the tide isrunning out from the box, the buoy should be taken in at the stern, theboat being held in position by the raising rope of the distribution boxand then by the multiple cable. The anchor rope is finally made fast inthe bow. During the planting of mines a man should always stand readyto slacken away on the anchor rope if necessary.

[Pg 53]If the buoy for the distribution box is not in place, the cable must beunderrun, either from shore or from a buoy planted for this purpose.This is done preferably with a yawl. The cable is raised, taken aboard,and placed over a roller or rowlock in the stern. The cable is thenpulled in over the stern and lowered over a roller or rowlock in thebow. If the planter is to underrun cable, a cathead is put in placeand a snatch block is lowered by a raising rope secured to a hoistingwindlass. The cable is placed in the snatch block and the planter movesforward slowly. When it is desired to transfer the cable to a smallboat the snatch block is lowered into the boat and the cable removed.

After the distribution box boat has secured the box in position,the lid is removed and the cable is tested as prescribed on page44. A signal is then raised to indicate to the planter that thedistribution box boat is ready for the planting of mines.

Planting the mines.—If there be a strong tide, the minesshould, if possible, be planted at such time that the planter, in goingout toward the line of mines, moves against the tide.

The planter moves out and passes close to the distribution box boat,with the latter to port. As it passes slowly by, a heaving line isthrown by a man forward of the beam to the distribution box boat, whoseparty immediately hauls in the mine cable, bends on another heavingline, and lashes the cable to the boat. It is desirable to have asecond heaving line ready in case the first one fails. If the water berough the cable end is passed to the boat by a launch.

The planter moves forward to the position to be occupied by mine No.10. If automatic anchors are used, the distance weight is lowered atthe command “Lower weight,” given after the cable is secured in thedistribution box boat. As the planter approaches this position the[Pg 54]command “Get ready” is given. As the forward davit comes abreast of theposition of No. 10 mine, the officer in charge of the planting commands“Let go”; the tripping hook of the mine is released first and that ofthe anchor immediately thereafter. The mine buoy, cable, and raisingrope are then thrown overboard.

(Caution.—The men operating the tripping hooks must be very carefulthat they stand back of all cable and rope, so that they may not becaught. All others must stand clear.)

The planter turns so that the stern will be thrown away from theplanted mine. When the stern is clear of the mine buoy “All clear” issignaled from the stern.

The planter then executes a sweeping circle to starboard, passes tothe rear, and comes up with the distribution box boat to starboard. Asit moves by, the free end of mine cable No. 9 is passed to the boatand secured as before. The planter moves ahead to a point 100 feet tothe left of mine No. 10, and as it crosses the line, plants mine No.9, swings off to port, circles and comes up from the rear with thedistribution box to port, and so on alternately until all the mines areplanted.

As soon as a mine is dropped the detail for that side of the planterprepares another for planting. There is ample time to do this while thevessel is turning and planting the other mine.

Two small boats, one on each side of the line, work as follows: As soonas a mine is dropped the boat on the corresponding side moves to it,picks up the buoy, pulls the rope taut, notes the submergence of themine, transmits the data to the planter, and holds up an oar or a flagin prolongation of the buoy rope. The observers at the ends of the baseline take observations on this marker and are thus able to plot theposition of the mine accurately. This process is repeated for each mine.

These boats also serve as guides to the planter in dropping mines byholding on to their buoys until the adjacent mines are planted. Withautomatic anchors the line may not be marked otherwise than in this manner.[Pg 55]

After the mine is dropped, the members of the distribution box boatparty remove the lashing from the cable, insert the Turk’s-head in theproper slot, make a temporary joint between it and the correspondingconductor of the multiple cable, and telephone to the casemateoperator. The latter opens all the power switches on the correspondingoperating board, closes switch No. 7 up (this throws D. C. power onthe mil-ammeter lead), and then plugs in on the upper jaw of thepower switch of the mine under test. If the D. C. voltage be 110, themil-ammeter should read about 40 mil-amperes; if the voltage be 80, thereading should be about 30. If this test be satisfactory, the joint ismade permanent.

For the last mine the telephones are removed from the correspondingconductor, a temporary joint is made in the boat, and the test madeas above. By arrangement with the casemate operator the mine is lefton two minutes for test. At the end of this time the joint is openedand the telephones put back. If the casemate operator reports the testsatisfactory, the telephones are again removed and a permanent joint ismade.

When the last joint has been made, the distribution box is closed andthe raising rope fastened to its lid. The box is then lowered. This isdone by the distribution box boat if it is provided with the necessarydavit and power, otherwise it is done by the planter. Generally theanchor rope is made fast to a buoy by a bowline, and the raising ropeof the distribution box is secured to the bight of the bowline.

After the distribution box is lowered all buoys are removed except thatfor the box, and such others as it may be desired to place for markingthe ends of lines. The marking boats may remove the mine buoys as theywork, provided they are notified from the mine commander’s station thatproper observations for plotting have been obtained. Such notificationis usually sent by telephone to the distribution box boat.

In time of war decoy buoys judiciously placed would be very useful indeceiving the enemy.

After the mines have been planted the following tests are made daily,or more frequently if need be, the results being recorded carefully onthe form given at the end of the chapter. (Note: This applies also tosuch test mines as may be kept planted for purposes of observation andinstruction.)

Caution.—If A. C. power be supplied from the casematemotor-generator, there is no possibility of accidental firing ofmines if the motor-generator is not running; and when it is runningthe chance is remote, since it would require the committing of threeblunders. However, the following precautions must be enforced rigidly:

1. Test of the D. C. voltage.—Plug in at the proper receptacleand read the voltmeter.

2. Test of the A. C. voltage.—Caution.—First seethat all automatic switches are up, that the firing switches are open,and that the A. C. operating switch No. 8 is open.

Close switch No. 4 up; close starting switch of motor-generator, andwhen the latter has attained its full speed close switch No. 9 up; plugin at the proper receptacle, and read the voltmeter. When the source ofpower is the storage battery, the battery rheostat should be adjusteduntil the A. C. voltage is 500 or above; when the casemate generator isused, its field rheostat should be adjusted for the same purpose.[Pg 57]

3. Test of the mines.—Leakage in mine circuits will beindicated automatically by an increased brightness of the green lamp onthe signal block; an excessive leakage in any mine circuit may causethe automatic switch to trip.

However, each mine should be tested separately, as follows:

With the D. C. on the D. C. busses of the power panel, close switch7 up, open the power switch on the mine block of the mine circuit tobe tested, and put the M-AM “plug” on the upper point of the powerswitch. If the automatic switch falls, adjust the solenoid or hold theswitch up while testing the circuit, otherwise the reading obtainedwill be that of the red lamp and bell circuit. These operations put themil-ammeter and its protective lamp in series with the mine circuit.

The circuit is as follows: From the negative D. C. bus on the powerpanel, to switch 7 closed up, through the mil-ammeter and itsprotective lamp, to the terminal bar, to the M-AM lead, to the plug,to the upper point of the power switch P, through the solenoid, to themiddle of the testing switch T, to the upper point of same, to theupper point of the automatic switch, to the middle of same, to the mineswitch, through same, to the terminal bar, through the 19-conductor andthe single-conductor cables, to the mine transformer primary, to themine case, to ground, to the D. C. “earth” terminal on the power panel,to switch 7, and to the positive D. C. bus on the power panel.

With from 80 to 110 volts these readings should normally be between 30and 40 mil-amperes. A mine may be fired if the reading with 80 volts isbetween 14 and 120 mil-amperes. These limits increase with the testingvoltage. If the mine tests within the firing limits, the solenoidshould be adjusted if the current is above its normal setting (0.075amperes). If the test indicates that the mine can not be fired, themine switch should be opened.

4. Test of the automatic switch, red lamp, and bell.—Throw theD. C. power on the busses of the operating board by closing switch 3up. Open the bell switch. Next close the testing switch down on the[Pg 58]mine block under test. The red lamp should glow and the correspondingautomatic switch trip. (For circuit see fig. 18.) Now close the bellswitch, throwing the bell in parallel with the red lamp; the bellshould ring. Next open the bell switch and repeat the test for eachmine block in turn.

5. Test of the alternating circuit.—This circuit is testedwith D. C., as follows: Connect the A. C. and D. C. jaws on the masterblock with a jumper, open the power switches, close switches 3, 8, and9 up on the power panel. The green and white lamps of the operatingboard under test should glow. A break or an excessive resistance in thecasemate grounds, or elsewhere in the circuit, will be indicated by thelamps not glowing, or glowing dimly.

The circuit is as follows: From the negative D. C. bus on the powerpanel, to switch 3, to the “operating board” terminal, to the D. C.lead, to the D. C. post on the signal block, through the green lamp, tothe D. C. jaw on the master block, through the jumper, to the A. C. jawon the master block, through the white lamp and resistance in parallel,to the A. C. post on the signal block, to the A. C. lead, to the A. C.“operating board” terminal, to switch 8, to the A. C. bus, to switch9, to the casemate transformer secondary, back to switch 9, to theother A. C. bus, back to switch 8, to the A. C. earth, through ground,to the D. C. earth, to switch 3, and to the positive D. C. bus on thepower panel. With this circuit on, remove the 90-ohm resistance inparallel with the white lamp; the white lamp should glow more brightly,indicating continuity of circuit through the resistance as well as thewhite lamp.

It will be observed that the above test is for only a part of the A.C. circuit. To test the firing switch and the lower contact of theautomatic switch, open switches 3, 8, and 9, close 7 up, remove thejumper, put the M-AM “plug” on the A. C. jaw on the master block, closethe firing switch, and trip in turn each automatic switch by raisingthe corresponding knob on the solenoid and observe the reading of themil-ammeter. Close each automatic switch up before tripping the next one.[Pg 59]

The mil-ammeter reading should be from 30 to 40 mil-amperes, indicatinga circuit through the firing switch and the automatic switch. Thecircuit is as follows: From the negative D. C. bus on the power panel,to switch 7 closed up, through the mil-ammeter and its protective lamp,to the operating board terminal, to the M-AM lead, to the “plug,” tothe A. C. jaw on the master block, through the firing switch F. S.,to the A. C. bus on the operating board, to the lower point of theautomatic switch which was tripped, to the middle of same, to the mineswitch, through the same, to the terminal bar, through the 19-conductorand the single-conductor cables, to the mine transformer primary, tothe mine case, to ground, to the D. C. “earth” post on the power panel,to switch 7, to the positive D. C. bus on the power panel.

6. Test of the delivery of the A. C. power to the operatingboard.—See that all the automatic switches of the operatingboards are up and all the firing switches of the master blocksopen. Close switches 4 and 9 up (or down) and 8 down; close thetesting switch T. S. on the master block. The white lamp should glowand the A. C. bus-bar voltage should drop appreciably.

The circuit is as follows: From the A. C. bus on the power panel,to the lower right terminal of switch 8, to the “operating board”terminal, to the A. C. lead, to the A. C. post on the signal block, tothe white lamp and the resistance in parallel, to the A. C. jaw on themaster block, to the testing switch T. S., to the “earth” post on thesignal block, to the earth lead, to the D. C. earth, through earth, tothe A. C. earth terminal on the power panel, through the choke coil, toswitch 8, to the other A. C. bus on the power panel.

In this test it is imperative to see that all the automatic switchesare up and all the firing switches are open.

7. Test of the power.—Insert two fuses in multiple across thefuse leads from the power panel. Put the fuses in a place prepared forthe purpose outside of the casemate, so that there will be no dangerfrom flying fragments. With all the switches on the power panel open,[Pg 60]all the automatic switches up, and the firing switches on the masterblocks open, energize the D. C. busses of the power panel, closeswitch No. 4 up (or down), and close the starting switch; close switchNo. 9 up (or down); close switch No. 12 up (which connects the minetransformer secondary to the fuses); and, finally, close switch No. 11up (which throws the A. C. power on the mine transformer primary). Thefuses should explode.

If fuses are not available for this test, a low-voltage lamp or a shortpiece of fine wire may be heated to incandescence.

8. Test of grounds.—(a) “Separate” grounds shall bemade for the A. C. power and the D. C. power on the power panel. Theword “separate” as here used means actual connection to earth withoutmetallic contact of the earth leads. A convenient method of making aground is to connect to the armor of a cable running to salt water, abond being made in case the armor of the cable in the casemate doesnot reach water before a joint is made. If a cable armor is used forone ground, the other ground lead must go to earth without contactwith that armor. This may be accomplished by using the conductors of acable, the ends of which are grounded to an earth plate in salt water.

(b) Neither of the grounds made should have more than 10 ohmsresistance. To verify this, tests should be made as follows:

Close the double circuit breaker; close switch 7 up and plug theextension cord of the mil-ammeter lead of the power panel on the upperleft-hand terminal of switch 8, the mil-ammeter extension cords for theoperating boards being disconnected.

Ascertain the voltage across the mil-ammeter and lamp, and across thebus bars. Read the mil-ammeter.

From these readings the combined resistance of the grounds can bedetermined.

A table or chart may be prepared giving the resistances for varioustesting voltages and mil-ammeter readings.[Pg 61]

Mines should be raised in the reverse order from that in which theywere planted if the conditions of wind and tide are favorable. Witha cross tide or a strong cross wind, the mines should be taken up inregular order from one side so that the planter will not drift onto themine field.

A yawl or launch takes position at the outer mine on each side. Themine-buoy rope is hauled up taut in order to locate the exact positionof the mine. The boat holds fast until directed from the planter to letgo. While the anchor and mine are being taken aboard the planter, theboat remains off the bow to render assistance if necessary.

The distribution box is raised by underrunning the multiple cable, orby means of its raising rope if the buoy has not been removed. The boxis taken aboard the distribution box boat, the lid is removed, and themine cables, in turn, disconnected from the multiple cable. The planterpasses close to the distribution box boat. A heaving line which hasbeen made fast to the outer mine cable is thrown to the bow of theplanter. If this should fail, a man throws a heaving line from the bowof the planter. If the conditions be unfavorable for passing a heavingline, a launch may carry the line to the planter. The heaving lineattached to the cable is hauled aboard and the cable placed over thecathead. The planter then proceeds to underrun the cable. If the waterbe shallow, the cable is carried through a snatchblock to the aft deckand coiled, or it may be carried to a cable-reel forward. If the waterbe deep, or the cable can not be raised easily by hand, it is carriedthrough a snatchblock to the drum of a hoisting windlass and coiled as[Pg 63]before mentioned. (If placed on a cable-reel, the ends should beinsulated and tagged. Mine cables Nos. 1 to 9 should be placed on onereel and Nos. 10 to 19 on another, both reels being carefully marked.)When the raising rope is reached, it is carried with the cable over thecathead. The bight of the rope is hauled in quickly, carried through asnatchblock, and a few turns taken on the drum of a hoisting windlass.The rope is untied from the cable as soon as possible. If there bedanger of losing the rope, it should be made fast at once. The anchoris raised until within a few feet of the cathead. It is lifted aboardby means of the boom, or by the differential block on the anchor davit.

At the same time a man is sent over the side of the planter near themine davit (a rope ladder may be used) to secure the hook of thedifferential block in the sling attached to the maneuvering ring ofthe mine when it comes to the surface. To bring the mine to the properplace to accomplish this, a man should be ready to secure the mine-buoyrope with a boathook; other men should be ready to pull the mineforward, if necessary, by means of the cable. The mine is raised bythe differential block of the mine davit. It may be raised by the boomand fall; or by means of a tackle secured to the mine davit, the endof the rope running through a snatchblock to the drum of a windlass.The distance weight of the automatic anchor may be raised by the fallof the boom, or by an improvised tackle. An eye should be made in thedistance rope for this purpose.

If the end of the cable is lost, the work may proceed as follows: Theplanter moves out to the mine if its buoy is still in place. A slingmade of raising rope may be thrown over the mine, or two raisingropes are tied together and one end is passed to a launch which movesaround the mine and brings the end back to the planter. Both ends areplaced over the cathead, through a snatchblock, and around the drumof a hoisting windlass. The mine is hoisted, bail up, until near thecathead. It can then be transferred to the anchor davit. The mine cableis pulled in until the raising rope is reached. The work then proceeds[Pg 64]as before. If the mine buoy has been removed, a yawl may drag for thecable with a grappling iron. If the raising rope should break or belost, the mine may be raised as mentioned above, except that the minemust be transferred to the fall of the boom and the anchor raised bymeans of its mooring rope, or the mine may be transferred to the anchordavit, as before, and a raising rope made fast to the mooring rope ofthe anchor and carried over the cathead, through a snatchblock, to ahoisting windlass. The mine, as soon as the strain is taken up by theraising rope, is unshackled. The anchor is then taken aboard in theusual manner.

As soon as the mines are taken aboard they are disconnected, theropes are coiled, and all matériel placed so as not to interfere withsubsequent work. As soon as the matériel is unloaded on the wharf itshould be cleaned thoroughly and stored.

If the multiple cable is to be left down, the ends of the conductorsare insulated, the lid replaced, and the box lowered by means of araising rope, the end of which is made fast to the bight of the bowlineof the anchor rope.

If the multiple cable is to be taken up, the end is passed to theplanter, run through a large snatchblock on the bow, and coiled on acable-reel as it is raised. Whenever a multiple cable is coiled on areel it should be secured so that both ends will be available for testwhen the cable is stored.

Unloading mines.—Should any of the mines be loaded withdynamite the utmost care must be exercised in unloading them.(See p. 76.) Some contrivance must be rigged upso that the first few turns of the compound plug may be accomplished bythe operator at a distance, as there is great liability of explosion,due to leakage of nitroglycerin into the screw threads. After thecompound plug is removed the precautions to be observed are given inAppendix No. 1.

Should the mine be loaded with guncotton or trotol, no danger is tobe apprehended in unloading; the usual precautions in handling highexplosives must, of course, be observed.

A mine command consists of the mine groups and rapid-fire batteriesspecifically assigned for their protection, which are controlled by asingle individual.

The mine commander is in direct command of the elements of the minedefense during drill and action. His station is at the mine primary,which is connected by telephone to the battle commander’s station.He bears the same relation to the battle commander as do the firecommanders, and his duties are similar to theirs.

The mine commander is responsible that the property officer requestsfor all matériel necessary to carry out the approved scheme for miningthe harbor; he is responsible, further, that the property officer keepsthis matériel in proper condition for immediate service.

The senior company officer of the mine command is the property officerand obtains from the district artillery engineer all necessary matérielfor the mine defense. He has direct charge of the storeroom, cabletanks, loading room, wharves, boats, boathouses, and mining casemate.The personnel of the mine companies are subject to his orders forservice in connection with caring for and maintaining this matériel.

The officers of the companies of the mine command will be assigned bythe mine commander in accordance with their special fitness.

The enlisted personnel of mine companies will be divided into sections,detachments, and details, as follows:

• (a) Fire-control and power section.
• (b) Planting and loading section.
• (c) Gun and ammunition sections.
• (d) Reserve section.

[Pg 66]These will be subdivided as follows:

• (a) Fire-control and power section:
• 1. Observing detachment—
• a. M′ detail.
• b. M″ detail.
• c. M‴ detail.
• 2. Plotting detachment—
• a. Plotting board detail.
• b. Communication detail.
• 3. Power detachment—
• a. Casemate detail.
• b. Searchlight detail.
• (b) Planting and loading section:
• 1. Planting detachment—
• a. Planter detail.
• b. Small-boat details.
• 2. Loading detachment—
• a. Loading room detail.
• b. Explosive detail.
• c. Cable detail.
• (c) Gun and ammunition section:
• a. Gun details.
• b. Projectile detail.
• c. Powder detail.
• (d) Reserve section: As required.

In each company assigned to the mine defense, a permanent manning tablewill be made out and always kept up to date. A copy of this manningtable will be posted in the mine commander’s station. In addition,a copy of such portion of this table as pertains to any particularstation will be posted therein.

Plotting board.—The plotting board differs from that used forguns in that it requires no gun arm and corresponding attachments.Furthermore, since the distance at which mines are planted will ingeneral be small, the board, without any change in size, may be usedwith a much larger scale, say, 150 yards or even 100 yards to the inch,and the arms graduated accordingly.

The stations are manned during the planting of mines and the locationof distribution boxes, as well as during operations.

[Pg 67]For planting buoys signals may be made from the primary, from thesecondary, or from both, as conditions warrant.

Observations are taken on each mine as planted, the data are recorded,and the position of each mine is plotted.

During operations vessels may be tracked by the vertical or by thehorizontal method of position finding. If by the former, either thecommand “Fire” may be given when the vessel is on the cross wires ofthe instrument set at the range and azimuth of a mine, or the time fromany point to the instant of passing over a mine may be found by meansof the prediction ruler (see below) and thecommand “Fire” be given at the proper instant, as indicated by the stopwatch. For the horizontal base system the latter method must be used.

Prediction ruler (fig. 15).—This isa 10-inch white celluloid slide rule with a beveled edge. The slideis graduated in “Yards in 15 seconds,” and on the left and right ofthe runway, respectively, are a “Fire at time” and a “Yards to mine”scales. The beveled edge is graduated from the center outward in bothdirections with “0” in the center of the scale and “500” at either end.Each 50 and 100 has its value engraved on the scale.

Method of using.—Plot the position of the target for a15-second interval. With the beveled edge find the distance the targethas passed over during the interval; and also determine the distancefrom the last plotted position to the mine. Move the slide until thegraduation corresponding to the “Yards in 15 seconds” is opposite thegraduation corresponding to the “Yards to mine,” and read the “Fire attime” scale opposite the arrow on the slide. The reading will be thenumber of seconds from the last plotted position to the mine which thevessel is approaching. A stop watch is started at the time of the lastobservation on the target, and at the expiration of the time obtainedfrom the “Fire at time” scale the command “Fire” may be given.

Observation firing.—The mine commander’s station is connectedwith the casemate by telephone. At the command “Observation firing”[Pg 68]sent to the casemate, the casemate operator will see that allautomatic switches are up, and that all firing switches are open.He will then close the double circuit breaker, and switches 4 and 9,which will energize the busses of the power panel. At the command“Group ——, mine ——,” the operator will close switches 3 and 8on the power panel, thereby putting both D. C. and A. C. power onthe operating boards. At the command “Ready,” given from the minecommander’s station at the proper time, the operator will stand readyto trip the corresponding automatic switch. At the command “Fire” theautomatic switch will be tripped and the firing switch will be closed.Without delay, after the mine is fired, the firing switch and the powerswitch will be opened, the automatic switch closed up, and the mineswitch opened on the mine block.

If the mine is struck before the command “Fire” is given, the automaticswitch will fall, and the mine should be fired by closing the firingswitch unless there are positive orders to the contrary.

Contact firing.—For contact firing the mine system will be setso that a signal will be sent to the casemate and the mine will befired when the latter is struck by a passing vessel. This is the normalmethod of firing in actual service. At the command “Contact firing,”which may be given for all groups, or certain individual ones, thecasemate operator will see that all automatic switches are up, powerand mine switches closed, and firing switches open; he will thenclose the double circuit breaker, and switches 4, 9, 3, and 8 on thepower panel. This puts both D. C. and A. C. on the operating boards. Hewill then close the firing switches on all the boards or on such as mayhave been indicated. When a mine has been fired, the corresponding mineblock will be cut out.

If it is desired to delay the firing of a mine after being struck, thecommand “Delayed contact firing” is given. The operations are the sameas for contact firing except that the firing switch is closed by theoperator a short time after the mine has been struck or when directedto do so. After the mine has been fired the firing switch will beopened, and the corresponding mine block will be cut out.

The latest adopted explosive for submarine mines is trinitrotoluol,also called trotol. The commercial names for this explosive are trinol,trotyl, and triton.

Wet guncotton is used extensively for submarine mines and in emergencyother commercial high explosives may be employed, preferably dynamite.

Trotol is a fine crystalline yellow powder, much resemblingbrown sugar. It is manufactured by nitrating toluol. It is veryinsensitive to shock or friction, insoluble in water, very stable instorage, and very powerful when detonated. Its melting point is about81° C., its ignition point is about 197° C., its specific gravity inpowdered form is about 1.55; it has no dangerous chemical action onmetals.

The priming charge is a fuse can full of crystalline trotol.

Trotol is supplied in wooden boxes doubly lined with wax paper, eachbox containing about 50 pounds of explosive. The date of receiptat the post and the name of the explosive shall be painted on eachbox. The boxes should be stored in tiers with the marked end out,the bottom tier resting on skids. The explosive is not dangerous tohandle, but the same care should be observed in storing and handlingas with other high explosives. It should be stored in a perfectly dryplace, preferably in a magazine. If it is impracticable to store in amagazine, the explosive may be stored in the driest place availablewhere it is protected thoroughly from all fire risks. If from any causethe boxes of explosive are wet and there is reasonable assurance thatthe interior has become wet, a box should be selected and opened. Ifthe interior is wet, a full report of the circ*mstances shall be madeto the War Department. Boxes should be opened and the contents dried inopen air out of the direct rays of the sun.[Pg 70]

Trotol may be stored with wet guncotton, explosive D, and dynamite.

Inspection at posts will be limited to seeing that the rules forstorage and care are strictly observed. Technical inspections will bemade, when required, by the Ordnance Department.

Wet guncotton in the form of compressed cakes is supplied inboxes lined with zinc, the lid being screwed down upon a rubber gasketso as to prevent the loss of water by evaporation. Each box contains100 pounds of dry guncotton. In the lid is a small flush cap whichscrews down upon a rubber washer and closes a tube communicatingwith the interior of the box. Upon each box there is painted by themanufacturer the net and total weights. Shipping regulations requirethat guncotton should be wet with water so that the water is 20 percent of the weight of guncotton and water. This is too much water forfull detonation, and the guncotton upon receipt at a post should bedried out so that the weight of water is from 12 to 15 per cent ofthat of the dry guncotton. The guncotton is dried by opening the boxand pyramiding the guncotton on the lid and in the box so that therewill be free circulation of air between the cakes. The use of anelectric fan in this connection will ordinarily materially facilitatethe operation. By weighing pilot cakes it may be determined when theproper amount of water has evaporated. The guncotton is then repacked,lid screwed down, and the weight chalked upon the end of the box.The guncotton should be placed while drying so that it is not in thesunlight and should be handled with clean cotton or rubber gloves.

In addition to the regular monthly inspection the boxes are reweighedquarterly under the supervision of the officer responsible forsubmarine mine explosive, and the gross weight so found chalked uponthe end. Should any box show any decided decrease in weight the screwcap in the lid is removed, enough fresh water, preferably distilled orrain water, added to bring it up to its original weight, and the screwcap replaced.[Pg 71]

Magazines in which guncotton is stored should not be allowed to attaina temperature as high as 100° F. for any length of time.

Guncotton which is kept wet may deteriorate after long storage, butwill not become dangerous.

Wet guncotton can not be ignited by a flame, but gradually smouldersaway as the outer portions in contact with the flame become dried.

A brownish or reddish shade is sometimes seen in cakes of guncotton.This is due to the presence of iron in the wash water and does notindicate decomposition.

When storing guncotton in the magazine the piles of boxes should bemade so as to give free circulation of air and the greatest conveniencein handling consistent with the capacity of the magazine.

In the event of damage to any case, which may cause loss of water byevaporation, the contents shall be removed at once, repacked in aguncotton box which has been washed with soda solution, the properamount of water added to the contents, and the box closed. The grossweight shall be marked on the case. In repacking avoid as much aspossible handling the cakes with the bare hands. This is for theprotection of the guncotton from oil or acid of any kind. Clean cottonor rubber gloves are suitable covering for the hands when engaged onthis work.

If for any reason the cases are subjected to dampness sufficient tocause unusual deterioration of the cases, they should be removed fromthe magazine and dried, out of the direct rays of the sun.

Guncotton containing 12 or 15 per cent of moisture may be stored withexplosive D, trotol, and dynamite, but never with dry guncotton.

Empty cases, before being placed in storage, must be washed thoroughlyto remove all traces of guncotton.

For a charge of wet guncotton, the priming charge is dry guncotton.This may be either of crumbled guncotton or cakes made to fit the fusecan. The compressed primer cakes are supplied wet and bored with holesto receive the fuses and the loading wire.[Pg 72]

Should the supply of guncotton primers become exhausted fresh ones maybe prepared as follows: Two blocks of soft pine are used, one 3 inchessquare, the other circular and 2.9 inches in diameter. A cake of wetguncotton is clamped between these blocks. Using a fine joiners’ sawand the circular block as a gauge, a cylinder is sawed from the cake.The cylinder is then smoothed down with a rasp. Four of these areprepared for each charge and in each one of them a hole about ⁹/₁₆ inchin diameter is bored. While boring the hole the cake must be tightlyclamped between two pine blocks to prevent it from splitting; to insurethat all the holes will be in alignment it is advisable that the upperwooden block be provided with a ⁹/₁₆-inch hole and be thick enough toenable this hole to serve as a guide for the bit. The boring is donewith the ordinary bit, which must be sharp, so as to cut clean. Itis not safe to saw or bore a dry guncotton cake.

It is essential that the guncotton primer be thoroughly dry. Theprimers may be dried by exposure to the air or by means of drying ovenssupplied especially for the purpose. To air-dry a primer, it is placedon edge upon a shelf of wire gauze or netting which is hung up indoorswhere there is a free circulation of dry warm air. Drying shouldcontinue until weighings on two successive days show no appreciableloss. This may require a week or more.

In drying with an oven the cakes are laid on edge on the shelvesand the temperature of the oven is kept at about 100° F.; it shouldnot exceed 104° F. The heat is provided by means of a bank of lampsplaced under the hood and the current of warm air regulated by thesize of the lamp bank and the openings in the top of the oven. Underno circ*mstances must an open flame be used as a source of heat. Thedrying in this case also is continued until successive weighings ofsamples show no appreciable loss.

Whenever it is necessary to dry more than 50 pounds of guncottonprimers for immediate use the guncotton should be placed in the dryingoven and exposed to the action of an electric fan placed about 4 feetin front of the open door until the moisture content is reduced to[Pg 73]about 6 per cent, when the drying should be completed by the use of thebank of lamps as described in the preceding paragraph.

In each case, to test the dryness of the primers, take a cake and splitit in four or five pieces and detonate each separately with a fuse.

It has been determined that about 5 per cent of water is the maximumcontent for unconfined guncotton capable of detonation by a Du Pont No.30 fuse.

Priming charges are not to be prepared until just previous to the timethey are to be used in loading. When the primers have been dried, theyshould be kept in well-sealed jars unless they are to be used very soonafter drying, in which case they will be stored in assembled fuse cans;when thus stored the assembled fuse cans should be kept in a cool, dry,and secure room away from other explosives. If, however, the primersare to be stored for any length of time, two strips of blue litmuspaper are inserted between the cakes, which are inspected from time totime. If the litmus paper shows decided redness, it should be removedand fresh strips inserted. If these strips turn red in a few hours,the primers should be thoroughly wet with fresh water. In general, theperiod of storage will be short and no particular examination of thedry guncotton will be required.

Dry guncotton should be handled as little as possible, to preventcrumbling and scattering of guncotton dust. Finely divided guncotton isdifficult to remove by brushing and if allowed to collect about a roommay give serious trouble by flashing should a portion become ignited.This dust may be removed with a damp sponge or cloth.

Dry guncotton which is not used as contemplated shall be rewet with theproper amount of water and repacked.

Samples of each lot of guncotton issued to the service are preservedin the laboratory of the Ordnance Department for chemical test. Theseretained samples are subjected regularly to technical inspection andtest by that department to determine their condition as to stability.This will insure the detection of lots that are deteriorating andtheir removal from the posts or their destruction before they havedeteriorated to such an extent that they become dangerous.[Pg 74]

Dynamite.—Dynamite cartridges are packed ordinarily in sawdustin wooden boxes. Each cartridge is wrapped in paraffin paper. Thecartridges are arranged in the box so that when they are transportedall cartridges will lie on their sides and never on their ends. Usuallythe amount of explosive in a single package will not exceed 50 pounds.

The boxes must never be allowed to stand so that the cartridges will bevertical.

Like other nitroglycerin, dynamite freezes at about 40° F., and inits frozen condition is, under ordinary circ*mstances, less liableto explosion from detonation or percussion than when thawed, butmore susceptible to explosion by simple ignition. Should any ofthe nitroglycerin be exuded, the dynamite cartridges are much moresensitive to explosion by a blow.

It is important that dynamite cartridges be kept dry. If exposed to amoist atmosphere, there is a tendency of the water, condensed from theair on all exposed surfaces, to displace the nitroglycerin.

The cases should be raised from the floor on skids and the floorunderneath covered with clean sawdust. The sawdust should be removedfrom time to time, the old sawdust being burned in the open air.

Rubber gloves should be worn in handling this explosive, or in theabsence of rubber gloves cover the hands with grease and wear cottongloves. This is for the protection of the skin from the injuriouseffect of nitroglycerin.

Dynamite may be stored with wet guncotton, explosive D, and trotol.

Date of receipt at post shall be marked on each box.

The priming charge for dynamite is a pound of loose dynamite containedin a small bag which fits easily into the fuse can. In filling the bagrubber gloves must be worn. To insert the fuses the bag is opened andthe fuses embedded in the explosive, the choke being tied around thefuse wires.

At the monthly inspection all boxes shall be examined to see if theyare dry. If not dry, all shall be exposed to the dry air out of thedirect rays of the sun.[Pg 75]

The principal source of danger from dynamite is in the exudation ofthe nitroglycerin. Exudation is indicated by the presence of smallwhite, oily, lustrous globules of liquid, either among the particlesof dynamite or on the packages. If such globules are discovered, theymay be identified positively as nitroglycerin by absorbing a drop in apiece of unglazed paper, which should be placed on an anvil or otherpiece of metal, and striking it a sharp blow with a hammer. If it benitroglycerin, an explosion will occur. Another test is to set fireto the paper, and if the liquid be nitroglycerin it will burn with acrackling noise and a greenish-yellow flame.

If exuded nitroglycerin has stained floors or other material notreadily destroyed, the nitroglycerin may be decomposed and renderedharmless by washing with “sulphur solution.” This solution may bemade by boiling 50 pounds of lime in a barrel of water and addingpowdered sulphur until the solution will take up no more. This willrequire about 20 pounds of sulphur. The resulting bright orange-coloredsolution should be filtered and only the filtrate used. A suitablefilter for this purpose is a piece of thin cheese-cloth. Sodiumcarbonate may be used in the place of lime.

Dynamite may be destroyed by burning in small quantities at a time.Slit the cartridge with a knife, spread out the contents over somestraw or shavings, and ignite carefully. Do not attempt to burn frozendynamite.

Mine fuses.—These are regular commercial electric fuses, extraquality, and each contains about 25 grains of mercury fulminate. Fusesare supplied in pasteboard boxes containing 50 each, pasteboard boxesbeing shipped in suitable wooden boxes. They are supplied with longleads which are cut to proper length when the mines are loaded. Theymust not be stored with other explosives.

Loading mines.—In loading mines the following precautions are observed:[Pg 76]

Unloading mines.—Mines charged with trotol or wet guncottonmay be unloaded without danger; the compound plug being unscrewed, thecakes of wet guncotton are removed by hand, repacked in the originalboxes, a little fresh water added, and the boxes closed. If loaded withtrotol, the charge is poured out into the boxes, which are then closed.Trotol should be inspected carefully when removed from the case, andif there is indication that any of it has undergone a change while themine was loaded, a report should be made to the War Department.

In unloading mines charged with dynamite too many precautions cannot be taken. The mine should be held either in an opening in a raftor behind an earthen traverse and the compound plug removed by somearrangement which may be operated from a safe distance. If the mine hasbeen planted for some time the recovered dynamite is usually destroyed.Sometimes the interior of the mine case may be found coated with anextremely thin film of exuded nitroglycerin. This film may be destroyedby filling and thoroughly rinsing the case with “sulphur solution.”

(See also Artillery Notes, No. 12.)

The engine.—This is a horizontal, single-acting,single-cylinder kerosene engine, having a flyball governor andoperating on a four-stroke cycle. This cycle consists in turn of theexplosion on the first outstroke, the expulsion of the products ofthe explosion on the following instroke, the intake into the cylinderof a mixture of air and oil vapor on the following outstroke, and thecompression of this explosive mixture on the next instroke. This cycletherefore requires two complete revolutions of the crank shaft for onecomplete set of operations.

On one side of the cylinder near the closed end is a valve boxcontaining two valves, the air-inlet valve and the exhaust valve. Theair-inlet and the exhaust valves are actuated by separate levers, eachlever being moved by a cam mounted on a horizontal shaft, driven bythe crank shaft through worm gearing. This horizontal shaft makes butone revolution while the crank shaft makes two; thus the air-inlet andthe exhaust valves are each opened once every two revolutions of theflywheel.

At the back of the cylinder, in prolongation of its axis, is acast-iron box called the vaporizer, which is always open to thecylinder. Before starting the engine this vaporizer must be heated byan external lamp, so that it will vaporize the oil when it is firstpumped into it. After the engine has started running, the lamp is nolonger required, as the vaporizer is kept at a sufficient heat by theinternal explosions.

A small oil pump, worked by the air-valve lever, draws oil from the oil[Pg 78]tank under the engine and forces it into the vaporizer at the propertime. The oil, on its way from the pump to the vaporizer, passesthrough a valve box attached to the vaporizer; this valve box has twovalves in it, a horizontal one, kept closed by a spring which the oilforces open as it goes into the vaporizer; the other, a vertical one,also kept closed by a spring. Should the engine run too fast, thegovernor opens this latter valve and allows some of the oil to flowback to the oil tank through the waste pipe. This valve can also beopened by turning the little regulating handle, which will stop thesupply of oil to the vaporizer and thus stop the engine.

INSTRUCTIONS FOR WORKING.

Frosty weather.—If there is danger of freezing, on shuttingdown drain the water from the circulating pipes and cylinder jacket,and valve box if water-jacketed; otherwise they may burst or crack.

Caution.—Before starting, see that the co*cks which admit waterto the water jacket of the vaporizer valve box are open; that the co*ckon the main water pipe from the bottom of the water tank is open; thatthe water in the tank is above the upper circulating pipe; that thedrain co*ck is closed; and that the oil tank is filled with kerosene.Gasoline must not be used with this engine.

Heating the vaporizer.—Open the relief co*ck on top of theengine cylinder. Place the lamp on the stand under the vaporizer; fillthe lamp with oil by means of the filling pipe till the oil is 1 inchbelow the pipe; and put a piece of wick into the cups which are formedaround the pipes. These wicks, which should consist of a piece ofordinary asbestos packing, will last for several weeks. Place the lidof the vaporizer cover crosswise on the cover to allow the escape ofheated gas and air.

A little alcohol or kerosene should be poured into the cup under thecoil and lighted. The cups may be filled with kerosene by closing theair-escape valve and working the air pump. The pressure forces oil outthrough the vapor nozzle and it will run down into the cups. When this[Pg 79]is nearly burned out pump up the reservoir with air by the air pump.Oil will issue from the small nozzle and give a clear flame. When it isdesired to stop the lamp, turn the thumbscrew on the reservoir fillingnozzle to let the air out. Should the nozzle become choked it should becleaned with the small needles for that purpose.

The heating of the vaporizer is one of the most important things to beattended to, and care must be taken that it is hot enough at starting.The attendant must see that the lamp is burning properly and that agood clear flame is given off for from 5 to 10 minutes, according tothe size of the engine. If, however, the lamp is burning badly, it maytake longer to become heated sufficiently. It is important that thisshould be carefully attended to, for though the engine may start, ifthe vaporizer is not as hot as it should be the engine will run badlyand perhaps soon stop altogether. Failures of engines to run properlycan in most cases be traced to this source.

No time should be lost in starting the engine after the vaporizer hasbeen sufficiently heated, as the engine may not run satisfactorily ifthe vaporizer is allowed to cool after heating it. The lamp should beleft burning a few minutes after starting.

Oiling the engine.—Oiling the engine should always be doneduring the heating-up of the vaporizer.

See that the oil cups on the two main crank shaft bearings are fittedwith proper wicks and filled with oil. Adjust the lubricator on thelarge end of the connecting-rod and oil the small end which is insidethe piston.

Oil also the following: The bearings on the horizontal shaft and theskew gearing, the rollers at the ends of the valve levers and theirpins, the pins on which the levers rock, the governor spindles andjoints and the bevel wheels which drive the same, and the joints thatconnect the governor to the vertical valve of the overflow. For suchbearings none but the best engine oil should be used.

It is necessary that a suitable oil should be used for lubricating the[Pg 80]cylinder, and unless such an oil be used for this purpose the enginemay run badly and perhaps stop altogether. Under no circ*mstancesmust a thick cylinder oil be used, and the oil must not be used overagain on the piston. Do not use ordinary lubricating oil. A high-gradegas-engine oil especially suited to this engine should be used and thepiston should be kept flooded with it.

Starting the engine.—Throw the hand lever to “To start.” Turnthe small crutch-handle regulator Y to the position “Shut” and work thepump lever up and down until oil is seen to pass the overflow freely.Turn the regulator back to “Open,” work the pump lever up and down afew strokes. Vapor should issue with some force from the relief co*ckon the cylinder. This indicates sufficient heat. Close the reliefco*ck and pump a few strokes. Man the flywheel and start the flywheelbackward, using the weight of the body if necessary, bringing thepiston up against compression as sharply as possible, and then releasethe wheel, when an explosion should take place and the engine startforward. As soon as the engine has sufficient speed to carry it pasta full compression, throw the lever to “To work.” When full speed isobtained, cut down the pump stroke to correspond to the load, open theoil feeders, and go over the engine carefully, seeing that the cylinderoil feed is working.

Oil pump.—When the cylinder is working at its full power thedistance between the round flanges on the pump plunger should be suchthat the hand gauge (supplied with the engine, and to be found in thetool box) will allow the part stamped “1” just to fit in between theflanges; if at any time the positions of these flanges be altered theycan be readjusted to this gauge. The other lengths on the hand gaugeare useful for adjusting the pump to economize oil. When running on amedium load, use length marked 2; on a light load, use length marked 3.See that the pump packing is not too tight.

Running the engine light.—When the engine is to run light—thatis, with no load or with a light load—it is best to alter the strokeof the pump to the amount of oil that will keep the engine running.This amount can be reduced so that the speed of the engine is a few[Pg 81]revolutions under the normal, which will allow the vaporizer to get asmall charge each time and keep it from cooling. The co*ck on the returnof the water circulating pipe may be nearly closed to keep the cylinderwarmer. These remarks do not apply when the load is intermittent andthe engine is running light for a short time only.

Air-inlet and exhaust valves.—See that the air-inlet and theexhaust valves are always working properly and drop onto their seats.They can at any time, if required, be made tight by grinding with alittle flour of emery and oil.

To insure a good seat to the valves when the stems are expanded by heatthe stems should clear the set-screws on the levers at least ¹/₁₆ inchwhen the air and the exhaust levers are clear of the cams. A greaterclearance is undesirable, as it prevents the full opening of the valves.

If at any time the air-inlet or the exhaust valves appear to be openingor closing at the wrong time, take off the nut on the end of the layshaft which holds the skew-wheel on and see that the chisel cuts on theshaft are opposite to one another. The lay shaft is coned where theskew wheel is fixed on and it is held on simply by friction, the nutbeing tightened against it.

Should it at any time become necessary to take out the crank shaft,always be sure that the skew-wheel gearing is put together so that thetooth marked “0” on the crank shaft skew-wheel fits in between the twoteeth marked “0” on the oil-shaft skew-wheel.

Vaporizer valve box and pipes attached to vaporizer.—Inthis box there are two valves. The vertical one is regulated by thegovernor, and when the engine runs faster than its proper speedthe governor pushes it down, thus opening it and allowing some oilto return to the oil tank. The horizontal valve in this box is aback-pressure valve. If at any time this valve is not working properly,vapor will be seen coming out of the overflow pipe; in this case thevalve should be examined. By screwing off the outside cap the tail ofthis valve can be seen; if the valve is turned around a few times it[Pg 82]will probably dislodge any dirt that may be under it; if, however, thisdoes not stop the leakage the valve should be taken out for inspection.

If the horizontal valve and sleeves are taken out at any time, greatcare must be taken in replacing them to use the same thickness ofjointing material as before or the distance the valve opens will bealtered.

See that the pipe from the pump to the vaporizer valve box is inclinedupward all the way from the pump. If this is not so, an air pocket willbe formed in which a certain amount of air will be compressed upon eachstroke of the pump. This will cause the oil to flow in slowly and notsuddenly as it should. If the oil tank be emptied of oil at any time,air will get into the suction and delivery pipes of the pump and itwill take some time before the oil going through the pump and pipeswill be free of this air; for awhile thereafter, the engine will notwork properly, as the air, by being compressed as the pump works, willinterfere with oil being pumped in suddenly. It is best, if the oilgets below the filter in the tank, to work the pump by hand for about10 minutes, holding the relief valve (on the vaporizer box) so as toget air well out of the pipes.

To stop the engine.—Turn the crutch-handle regulator to “Shut.”Close the automatic lubricator. If it is desired to stop the engine fora short time only, put the lamp back under the vaporizer to keep it hot.

Setting the oil engine and the generator.—The engine andgenerator should be so located that the distance from center to centerof pulleys should be as nearly correct as possible when the generatoris at the middle point of the base rails, so that the proper tension ofthe belt may be obtained within the limits of adjustment allowed by therails.

The two pulleys should be accurately in line and the belt not tootight. The generator base should rest on a wooden frame to separate itfrom the concrete pier. Both engine and generator should be held firmlyin position by anchor bolts.

For the generator bearings a quantity of the best dynamo oil is[Pg 83]furnished; the commutator should be clean and smooth, and the brushesshould fit the surface. The commutator should be cleaned occasionallywith a little paraffin on canvas, and the brushes should be adjusted,so that when running at full load no sparking occurs.

All electrical connections should be firmly made and kept thoroughlyclean. A cover should be kept on the generator when not in use. If themachine be damp it should be allowed to dry before running at full load.

Note.—A few new installationshave been supplied with 5-kw. gasoline electric sets, and futureinstallations will be similarly equipped. Wherever installed, pamphletson the care and operation of the gasoline sets have been furnished,containing full instructions for the guidance of those concerned.

(See pamphlets issued by the Electric StorageBattery Co., Philadelphia, Pa., on General Instructions for theOperation and Care of the Chloride Accumulator.)

Unpacking material.—Great care should be taken in the unpackingand subsequent handling of the various parts of the battery, as many ofthem are easily broken or bent out of shape by rough handling.

Open the crates or packing boxes on the side marked “Up” and carefullylift contents out; never slide them out by turning the crate on itsside.

Upon opening the crates and boxes, carefully count the contents of eachpackage, and check with the shipping list. A number of small parts willusually be found in each shipment, and care should be taken to examinethe packing materials to determine that no parts have been overlooked.

Immediately upon opening the crates the materials should be carefullyexamined for breakage. Cracked jars, whether of glass or rubber, shouldnot be set up, for if put into use leakage of electrolyte may causeannoyance or trouble.

Location of battery room.—The proper location of the batteryis important. It should be in a separate room, which should be wellventilated, dry, and of moderate temperature. Extremes of temperatureaffect the proper working of a battery. The air should be dry, for ifdamp there is danger of leakage due to grounds.

The ventilation should be free, not only to insure dryness, but toprevent chance of an explosion, as the gases given off during chargeform an explosive mixture if confined. For this reason never bring anexposed flame near the battery when it is gassing.[Pg 85]

Direct sunlight should not fall on the cells.

The trays, the benches on which the cells rest, and all metal work(iron and copper) should be painted with asphaltum varnish.

Assembling and placing cells in position.—Place the jars,after they have been cleaned, in position on the stands, which shouldbe provided for the purpose and which should be so situated in theroom that each cell will be easily accessible. The jars are set in thetrays, which previously should be filled with fine dry sand even withthe top, the trays resting on the glass insulators.

Place the elements as they come from the packing cases on a convenientstand or table (the elements are packed positive and negative platestogether; the positive has plates of a brownish color, the negativeof a light gray—the negative always has one more plate than thepositive), cut the strings that bind them together, and carefully pullthe positive and negative groups apart, throwing the packing aside.After carefully looking over both groups and removing any dirt or otherforeign matter, assemble them, with separators between each positiveand negative plate.

When putting into the jars be careful that the direction of the lugsis relatively the same in each case, thus causing a positive lug ofone cell always to connect with a negative of the adjoining one, andvice versa. This insures the proper polarity throughout the battery,bringing a positive lug at one free end and a negative at the other.

Before bolting or clamping the lugs together, they should be wellscraped at the point of contact to insure good conductivity and lowresistance of the circuit; this should be done before the elements aretaken apart and directly after unpacking, if the battery is to be setup at once. The connections should be gone over and tightened severaltimes after the lugs are first fastened together to insure good contact.

Connecting up the charging circuit.—Before putting theelectrolyte into the cells, the circuits connecting the battery withthe charging source must be complete, care being taken to have thepositive pole of the charging source connected with the positive end ofthe battery.[Pg 86]

Electrolyte.—The electrolyte is dilute sulphuric acid of aspecific gravity of 1.210 or 25° Baumé, as shown on the hydrometer attemperature of 70° F.

The electrolyte should cover the top of the plates by one-half inch tothree-fourths inch, and must be cool when poured into the cells. Thejars should be numbered with asphaltum varnish and a line made with thesame material to indicate the height at which the electrolyte should bekept.

Initial charge.—The charge should be started at the normalrate as soon as the electrolyte is in the cells and continued at thesame rate, provided the temperature of the electrolyte is well below100° F., until there is no further rise or increase in either thevoltage or specific gravity over a period of 10 hours, and gas is beinggiven off freely from all the plates. Also, the color of the positiveplates should be a dark brown or chocolate and that of the negativesa light neutral gray. The temperature of the electrolyte should beclosely watched and, if it approaches 100° F., the charging ratemust be reduced or the charge stopped entirely until the temperaturestops rising. From 45 to 55 hours at the normal rate will be requiredto complete the charge; but if the rate is less, the time will beproportionately increased. The specific gravity will fall rapidly afterthe electrolyte is added to the cells, and may continue to fall forsome time after charging begins. It will finally rise as the chargeprogresses, until it is again up to 1.210 or possibly slightly higher.The voltage for each cell at the end of charge will be between 2.5and 2.7 volts, and for this reason a fixed or definite voltage shouldnot be aimed for. It is of the utmost importance that this charge becomplete in every respect.

At the end of the first charge it is well to discharge the batteryabout one-half and then immediately recharge it. Repeat this treatmenttwo or three times and the battery will be in proper working condition.

After the completion of a charge (initial or with the battery inregular service) and the current off, the voltage will fall immediatelyto about 2.20 volts per cell, and then to 2 volts when the discharge isstarted. If the discharge is not begun at once, then the pressure will[Pg 87]fall quite rapidly to about 2.05 volts per cell, and there remain whilethe battery is on open circuit.

Battery in regular service.—A battery must not be repeatedlyovercharged, undercharged, overdischarged or allowed to standcompletely discharged. After the initial charge is completed, thebattery is ready to be put into regular service.

A cell should be selected as a “pilot cell”; that is, one that is ingood condition and representative of the general condition of thebattery. The height of the electrolyte in this cell must be keptconstant by adding a small quantity of water each day. This cell is tobe used particularly in following the charge and indicating when itshould be stopped.

When the battery is in regular service, the discharge should not becarried below 1.75 volts per cell at full load. Standing completelydischarged will cause permanent injury; therefore the battery should beimmediately recharged after a heavy discharge.

In usual service, with the normal rate, it is advisable to stop thedischarge at 1.90 volts per cell. If the discharge rate is considerablyless than normal, the voltage should not be allowed to fall as lowas 1.90 volts per cell, for the reason that with a very low rate ofdischarge the voltage will not begin to fall off until the limitof capacity is almost reached. The fall in specific gravity of theelectrolyte also serves as an indication of the amount taken out and isin direct proportion to the ampere-hour discharge, thereby differingfrom the drop in voltage, which varies irregularly for different ratesand degrees of discharge. For this reason, under ordinary conditions,the fall in specific gravity is to be preferred in determining theamount of discharge.

The actual amount of variation in the specific gravity of theelectrolyte between a condition of full charge and a complete dischargeis dependent upon the quantity of solution in the containing vesselcompared with the bulk of the plates. When cells are equipped withthe full number of plates, the range will be about 35 points (0.035sp. gr.); for instance, if the maximum specific gravity reached onthe preceding overcharge is 1.209, the extreme limit beyond which thedischarge should not be carried is about 1.174. If the cells have less[Pg 88]than the full number of plates, this range in specific gravity isproportionately reduced, except in the case of the “pilot cell,” whichshould be equipped with a device for displacing the excess electrolyte.

The available capacity is temporarily reduced at low temperatures; witha return to normal temperature the capacity is regained.

The battery should preferably be charged at the normal rate. It isimportant that it should be sufficiently charged, but the chargeshould not be repeatedly continued beyond that point. Both from thestandpoint of efficiency and life of the plates the best practice isthe method which embraces what may be called a regular charge, to begiven when the battery is from one-half to two-thirds discharged, andan overcharge to be given weekly if it is necessary to charge daily, oronce every two weeks if the regular charge is not given so often.

The regular charge should be continued until the specific gravityof the pilot cells has risen to within five points of the maximum,as shown on the last previous overcharge. For example, if on theprevious overcharge the maximum is 1.210, then on the following regularcharges the current should be cut off when the specific gravity ofthe pilot cell reaches 1.205. The pilot cell method of noting the endof charge should not be used with a battery unless all the cells areapproximately in the same condition. With an old battery whose platesare not uniform, readings should be taken on each cell to determine theend of charge.

The overcharge should be prolonged until all the cells gas freely anduntil no rise in the specific gravity and voltage of the pilot cell isshown for five successive 15-minute readings.

Just before the overcharge the cells should be carefully examined tosee that they are free from short circuits. If any short circuits arefound they should be removed with a stick or a piece of hard rubber; donot use metal.

As the temperature affects the specific gravity this must be consideredand correction made for any change of temperature. The temperaturecorrection is one point (0.001 sp. g.) for 3 degrees change in[Pg 89]temperature. For instance, electrolyte, which is 1.210 at 70°, will be1.213 at 61° and 1.207 at 79°.

Inspection.—In order that the battery may continue in the bestcondition it is essential that specific gravity and voltage readings betaken on all cells in the battery at least once a week; the specificgravity readings on the day before the overcharge and the voltagereading near the end; the voltage readings must always be taken whenthe current is flowing, open circuit readings being of no value. Also,at the end of each charge it should be noted that all of the cells aregassing moderately and at the end of the overcharge very freely.

Unevenness of cells; cause and remedy.—If any of the cellsshould read low at either time and do not gas freely with the othersat the end of charge, examine them carefully for pieces of scale orforeign matter which may have lodged between the plates. If any arenoted, remove them by pushing down into the bottom of the jar with astrip of wood. Never use metal of any kind for this purpose.

If, after the cause of the trouble has been removed, the readings donot come up at the end of the overcharge, then the cell must be cut outof circuit on the discharge, to be cut in again just before beginningthe next charge, during which it should come up all right.

Impurities in the electrolyte will cause a cell to work irregularlyand the plates to deteriorate. Should it be known that any impurityhas gotten into the electrolyte, steps should be taken to remove it atonce. The solution should be replaced with new immediately, thoroughlyflushing the cell with water before putting in the new electrolyte.The change should be made when the battery is discharged, for theimpurities will be in the electrolyte when the battery is discharged.Immediately after the change the cell should be charged. If in doubtas to whether the electrolyte contains impurities, a half-pint sample,taken at the end of discharge, should be submitted for test.

Sediment.—The accumulation of sediment in the bottom of thejars must be watched and not allowed under any circ*mstances to getup to the plates; if this occurs, rapid deterioration will result. To[Pg 90]remove the sediment, the simplest way, if the cells are small, is tolift the elements out after the battery has been fully charged, drawoff the electrolyte, and then dump the sediment, and clean the jar withwater, getting the elements back and covered with electrolyte againas quickly as possible, so that there will be no chance of the platesdrying out. Electrolyte, not water, will be required to complete thefilling of the cells, the specific gravity being adjusted to standard(1.210 at the end of charge).

Evaporation.—Do not allow the surface of the electrolyteto get down to the top of the plates; keep it at its proper level(one-half inch to three-fourths inch above the top of the plates) bythe addition of pure water, which should be added at the beginning ofa charge, preferably the overcharge. It will not be necessary to addelectrolyte except at long intervals or when cleaning, as noted above.Electrolyte added to replace loss should be of specific gravity 1.210.

Battery used but occasionally.—If the battery is to be used atinfrequent periods, it should be given a “freshening” charge every two weeks.

Putting the battery out of commission.—If it is thought best toput the battery out of commission for a time, then it must be treatedas follows: After thoroughly charging, syphon off the electrolyte(which may be used again) into convenient receptacles, preferablycarboys which have been previously cleaned and have never been usedfor other kinds of acid, and as each cell becomes empty immediatelyfill it with fresh, pure water. When water is in all the cells allowthem to stand 12 to 15 hours, then draw off the water; the batterymay then stand without further attention until it is again to be putinto service; then proceed as in the case of the initial charge, asdescribed above.

If for any reason any cell becomes discharged before the others, itshould be cut out on discharge and worked up to normal before beingused.

Should the battery sulphate, charge and discharge frequently, not usingless than one-half normal rate at any time and increasing to full rate[Pg 91]as the plates show signs of recuperation; keep the temperature of thecells below 100° F. Frequent exercise will clear the plates in a badlysulphated battery.

Keep careful records of all charging voltages, specific gravities, andtroubles with the cells.

The following is a recapitulation of the important points in operatinga storage battery:

CONDENSED INSTRUCTIONS.

Submarine mine cable is shipped on reels having an outer sheathing forprotection in transit, with at least 12 feet of both ends of the cablebrought out and coiled on the head of the reel for test purposes. Ifthe cable is not for immediate use, it should be moved to the cabletank, and by means of the overhead trolley and cable tongs put in itsposition in the tank, the two ends being properly tagged and firmlyfixed so as to allow it to be tested. In arranging the multiple cablein the tanks that which is to be used first should be most readilyaccessible.

The cable tank should be provided with a cover to keep it clean, aswell as to lessen as much as possible variations of temperature. Enoughclean water to cover by several inches the outer sheathing of the cablereels should be kept in the tanks, but in climates where the water inthe cable tanks would normally freeze to a depth exceeding 2 feet, thewater should be let out of the tanks before ice begins to form andnot again admitted until the following spring. In localities wherethe tanks may become a breeding place for mosquitoes, as a preventivemeasure, salt water from the ocean or bay should, when practicable, beused for filling the tanks, or where it is necessary to use fresh watersufficient salt should be added to produce a 3 per cent solution. Nooil or kerosene should be used in the tanks.

The methods of recording tests and of classifying and transferringsubmarine mine cable are prescribed by orders from the War Department.The tests of submarine mine cable at posts will consist in determiningthe insulation and conductor resistances.

The insulation surrounding the conductor of a cable is supposed to be[Pg 93]uniform in regard to quality of material, density, and thickness. Theresistance which it offers to the passage of a current through it willthen vary inversely with its length. In comparison the insulationresistance of 1 mile of cable is taken as the standard. This insulationhas a large negative temperature coefficient; that is, an increaseof temperature lowers its resistance. It is customary to reduce allinsulation resistance to that at a standard temperature of 60° F.,and for this purpose reduction factors applicable to the particularinsulation compound should be furnished with the cable. (Note: It hasbeen found that for most compounds, if the logarithms of the resistanceare plotted as ordinates against the temperature in degrees F. asabscissæ, the resulting curve will be very nearly a straight line.)

The ordinary methods of measuring resistance—that is, by means of aWheatstone bridge, or by fall of potential, or by voltmeter—can notbe used in measuring resistance as high as that of the insulation of asubmarine cable. For this the direct deflection method is employed.

In brief, this consists of the following steps:

First. The deflection produced in a galvanometer by a current froma battery through a known resistance, usually 100,000 ohms, isdetermined, whence is calculated the resistance through which this samebattery would produce a deflection of one point using the unity shunt.This is expressed in megohms and is called the galvanometer “constant”under the conditions.

Second. The deflection produced by the current from the same batterythrough the insulation of the cable is determined, whence, from“First,” the corresponding number of megohms is calculated.

Third. This multiplied by the length of the cable in miles andcorrected for temperature gives the required insulation resistance permile.

This testing can be made most satisfactorily on dry days, but a closeadherence to the instructions herein given relative to the preparationof the cable ends, the insulation of the cable lead and of the battery,and the drying out of the test room and instruments should enable[Pg 94]satisfactory work to be done under adverse conditions of weather orclimate. The following apparatus is required: Reflecting galvanometer,universal shunt, special testing key, 100,000-ohm resistance box,battery of dry cells giving approximately 100 volts, and stop watch.

Figure 16 shows diagrammatically thearrangement of the apparatus for testing a reel of cable. As a rule theinstruments should be so placed that one person may manipulate the keyand the shunt while at the same time observing the galvanometer.

The 100,000-ohm box, as a protection to the galvanometer in testing, isalways kept in the circuit and its value should be subtracted from theresistance determined, except in the case of high insulation resistancewhen it will not be necessary to make the subtraction.

The universal shunt is always employed with the galvanometer and isused both to vary the current through the latter and to protect it froma violent throw at the instant of making or breaking the circuit at thetesting key. This last is accomplished by having the shunt on zero atsuch times.

The galvanometer being a very sensitive instrument must be solidlysupported so as to be free from jars or vibrations.

The special testing key, shown diagrammatically in the figure, has itsbinding posts plainly marked. It is a double-throw key and has twopositions upon each side. When completely closed to the right, thecable is charged through the galvanometer from the positive pole; whento the left, from the negative pole of the battery. In each case thedeflection of the galvanometer is in the same direction. When partlyclosed on either side, the cable is discharged to earth through thegalvanometer. (Note: It will be observed that the connections are suchthat the galvanometer is always connected to the cable core and neverto the ground. With this connection, so long as the lead PX is freefrom leaks or grounds, the galvanometer measures only the currentactually passing through the core and not that leaking through anyimperfect insulation in the battery and leads.)

Cable testing is a very simple operation, but extreme care is necessaryin all operations.

[Pg 95]The following is a detailed description:

I. Preparing the cable for testing.—1. Closely examineeach conductor end. Look particularly for unusually hard orbrittle insulation and for torn, pinched, or punctured insulation,especially near the ends of the armor wires. If any of the ends arenot in perfect condition, cut off enough cable to secure good ends.(Caution.—Do not cut off more than enough to secure good ends,for after three or four tests it may be necessary to unreel the wholecable to secure enough of the inner end above water.)

2. Verify the tagging. Remember that the “shore end” is the end fromthe outer coils on the reel and is numbered clockwise. The other end isnumbered contraclockwise.

3. The “ground” should be made by taking several turns of bare copperwire around the armor of the cable to be tested and soldering them inposition. One such ground in each tank is sufficient. Whenever “ground”or “earth” is subsequently spoken of, this ground in the tank is meant,and not a connection to ground at some point outside the tank.

4. The leads PX and BY (fig. 16) should beof loading or other heavily insulated wire. They must be carefullyinsulated from each other, from the ground, and from the walls or otherparts of buildings. This is especially true of the cable lead PX. Indamp weather porcelain-knob insulators and porcelain tubes (the latterfor use in passing through walls or partitions) may not be sufficientto afford proper insulation for the cable lead. In such case thelatter should be suspended in the air from the testing switchto the cable tank by means of several chains of paraffined porcelaininsulators suspended by marline or protective tape which has beenboiled in paraffin. These suspensions should be in each case undercover and should be kept as dry as possible. The length of the leadsis immaterial. If loading wire is used, the distance between supportsshould be short (not over 50 feet), as this wire stretches considerablyfrom its own weight, pulling out the insulation and giving a very thinwall, particularly at points of support. Extreme care should be takento tighten up on the knob insulators, in case they are used, justenough to hold the wire without pinching the insulation.[Pg 96]

5. Using a double connector, join the lead BY to the ground wire on thecable above the surface of the water. Put a connector on the end of theother lead so that it can be readily attached in turn to each conductor.

6. Any protective covering, such as armor, jute, etc., should beremoved from the ends of the conductors for a distance of about 12inches, thus laying the insulation coating bare. This latter shouldnot be handled and must be kept scrupulously clean. With a cleandry knife prepare each conductor of the cable to be tested bycutting off about 1 inch of the insulation from each end of the wireand then tapering the end of the insulation for about 1 inch, leaving aperfectly clean surface. In damp weather dip each end of each conductorinto melted paraffin (not boiling, but heated above 212° F.). Secureone end of the cable so that it is well separated from the surroundingobjects and separate the conductors so that no ends are touching.

7. Take one strand of a loading wire about 4 feet long and wrap ittwo or three times around the projecting copper end of each conductorat the other end of the cable, then connect it to earth. See that theconductors at this end are dry. Leave the lead PX disconnected andsuspended in the air.

II. Setting up the testing apparatus.—1. Select a light, dryroom as near the cable tank as practicable.

2. Use dry cells for the battery. The voltage of the battery should besuch as to give a full scale deflection of the galvanometer through theresistance employed for taking the constant (with shunt at ¹/₁₀₀₀).Large galvanometer throws are essential for reliable results.

Set up the cells on shelves in a small closed closet or box, withnarrow strips of wood or heavy cardboard laid between each row ofcells, lengthwise and crosswise. The height of each strip should beabout half the height of a cell, so that the two layers of strips willcome nearly to the tops of the cells and keep them well separated.Wire the cells in series and bring the terminals out to a double-polesingle-throw switch, which should be on a heavy porcelain or slate base[Pg 97]and rated for at least 250 volts. (It may be found desirable to installsome electric lamps in the closet to keep the battery dry.)

If difficulty is experienced in eliminating grounds from the batteryset up in this manner, the battery box should be suspended in air bymeans of chains of paraffined cleats.

3. Set up the galvanometer on a pier or on a window sill if thebuilding is of masonry. It should be insulated by placing its feet on aslate or ebonite slab, or in glass insulators. Remove the cover. Adjustthe level until the suspended coil hangs freely. Maneuver the suspendedcoil, by means of the knob at the top of the tube, until its face isparallel with the face of the instrument. Then adjust the level untilthe upper suspension hangs in the center of the supporting tube, andthe air gap between the coil and armature is symmetrical. Replace thecover. Put on the scale and the telescope. Turn the mirror so that itreflects the 0 of the scale approximately, getting exact adjustment bymoving the scale. Be careful (particularly in dry weather) not to touchthe glass of the cover or to do anything which will produce a staticcharge on the glass.

The galvanometer scales are usually graduated in equal divisionscorresponding to 1 millimeter on the circumference of a circle whoseradius is 1 meter. Each tenth division is usually marked with a number.This number is sometimes 1 instead of 10, 2 instead of 20, and so on.The number of divisions to read and record is the number of smallest(millimeter) divisions. Do not try to read closer than ½ of onedivision. The larger the throw the less the personal error. No accurateconclusion can be drawn from a very small throw.

4. Place a table or low shelf conveniently to one side and place theshunt, the testing key, the ⅒ megohm box, and a voltmeter on it. Theapparatus should be insulated by an ebonite or slate slab, or glassinsulators. Fasten the shunt and the key securely to the table or theshelf. (The use of paraffin paper for insulating instruments is a makeshiftat best. It soon gets soiled and creased, then it has to be replaced.)[Pg 98]

The use of lamps to keep the apparatus dry may be desirable, or itmay be found convenient to expose the apparatus to the sun for afew minutes before beginning the test on any day. The use in thetesting room of a small stove or of a gasoline torch for two or threehours before the beginning of the testing will ordinarily prove veryadvantageous.

5. Wire up as in figure 16, except that theleads from the testing key should be carried to the battery through thedouble-pole single-throw switch above referred to. (The battery switchshould be opened whenever any connections are made or altered.) Allleads used in connecting up the instruments should be of heavy copper,and stiff enough to hold permanently any shape to which they are bent.They should be supported at points of connection only, and should notlie on the table or within an inch of each other.

III. Testing the insulation of the apparatus.—1. Voltmetertest of battery insulation.—This is a rough test, but should beincluded. A serious ground can be much more quickly located with avoltmeter than with the galvanometer.

(a) Disconnect the battery leads at the battery switch; connect+ lead of battery to + post of the voltmeter; connect the B end of thelead BY to - post of the voltmeter; - lead of the battery should be inthe air. Close the voltmeter switch and read.

(b) Disconnect the voltmeter. Connect - lead of the battery to- post of the voltmeter. Connect the B end of the lead BY to + post ofthe voltmeter; + lead of the battery should be in the air. Close thevoltmeter switch and read.

If any deflection is obtained in either case, the battery or itsconnections are grounded. Locate and remove the ground. (See Foster orsome other practical handbook.)

2. Testing the battery voltage.—Connect the voltmeter acrossthe battery terminals. Read and record the voltage. (If there is novoltmeter available which will read as high as the battery voltage,take the voltage of the battery in sections and add, or make amultiplier of one of the resistance coils in the ⅒ megohm box.)[Pg 99]

3. Testing the battery and the apparatus for grounds with thegalvanometer.—With a camel’s-hair brush go over all theinstruments and carefully remove dust. See that the instruments andconnections are dry. Do not blow on the instruments.

Open the battery switch. Connect the battery leads to the batteryswitch. Disconnect lead PX at P and connect the earth leads BY andEY to the key at “cable post.” (Y is grounded.) Bothbattery leads are left connected to the key. The shunt should be on 0.Close the battery switch. Close the testing key to the right. Turn theshunt gradually to the unity post. The galvanometer deflection shouldbe zero. Turn the shunt to 0. Reverse the testing key. Turn the shuntto the unity post. The deflection should be zero. If any deflectionis obtained, there is a ground in the battery, the apparatus, or theconnections. The test of the cable should not proceed if a deflectionis obtained in either position of the key.

In reporting the voltage + to earth and - to earth as “zero” on form,it will be understood that this means zero using the galvanometer, asherein described.

4. Insulation of leads.—Turn the shunt to 0. Open the batteryswitch. Connect the earth leads BY and EY to their proper posts.Connect the cable lead, PX, to “cable” post. See that the cable tankends of the lead PX is disconnected at X and suspended in the air.Close the battery switch. Close the key and turn the shunt to theunity post. Deflections should be as small as possible and in anycase must be steady and uniform for several trials. Turn theshunt to 0. Reverse the key, stopping at the discharge position. Turnthe shunt to the unity post and wait until the galvanometer rests at0, indicating that the leads are discharged. Turn the shunt to 0.Close the key all the way down. Turn the shunt to the unity post. Thedeflection should not differ materially from that noted above. If thereis a deflection, the trouble is in the lead PX or its connections.Go over these, carefully examining for dust and moisture and notingparticularly the proximity of all wires of opposite potential whichcross or lie near each other. If there is a small deflection which can[Pg 100]not be removed, a correction must be applied subsequently to thedeflection obtained in the test for the insulation resistance of theconductor.

Using proper care, there are very few days when perfect insulationof the instruments can not be secured. The lead leakage withwell-insulated wire put up properly will be noticed rarely.

5. Use of Price guard-wire.—As an additional precaution againstsurface leakage across the insulation at the ends of the conductorit will sometimes be advisable to install an additional lead (notnecessarily as carefully insulated as PX) running from the testingswitch to the cable under test. This lead should be connected in at thetesting switch to the post carrying the lower blade between “D” and “C”(fig. 16); the tank end should be bare ofinsulation for a sufficient distance to enable the bare wire to bewrapped firmly, without pinching, around the insulation at each end ofthe particular conductor under test, just below the tapered portion.

The potential difference between the cable core and this guard-wireis thus made practically nil, so that any leakage will be from theguard-wire to the tank, consequently this leakage will not be measuredby the galvanometer.

IV. Take the galvanometer constant as follows: Open the batteryswitch.

With a short piece of wire connect the hinge post of the testing keymarked “cable” to either “earth” post of the key, the leads to thecable tank being disconnected at E, B, and P. Turn the shunt to 0.Examine the ⅒ megohm box and see that all the resistance coils arein the circuit. Close the battery switch and the testing key. Turnthe shunt to the ¹/₁₀₀₀ post. Watch the swing of the galvanometer andwhen it has come to rest, read and record. Turn the shunt to 0. Thegalvanometer should return exactly to 0. If it does not, readjust andrepeat until it does. The galvanometer constant is numerically equal tothe total throw in smallest divisions of the scale multiplied by100. Remove the connecting wire and replace the leads to the tank.[Pg 101]

If at any subsequent time during the test the galvanometer adjustmentis disturbed—that is, if it does not return accurately to zero whenthe shunt is at 0—the constant should be redetermined.

Testing the cable.—1. See that the testing key is open and theshunt at 0. Connect the earth lead to ground on the cable armor. Removethe earth connection from No. 1 conductor and connect the cable lead tothis conductor; in wet weather the connector joint should be dipped inmelted paraffin. (In using paraffin to insulate joints or ends bring itjust above 212° F. to evaporate any moisture present. It should not beboiling. The paraffin coating should be at least as thick as the rubberinsulation and extend back over the rubber for an inch or more.)

2. Close the testing key to the left (+ to earth), stopping at thedischarge position, and turn the shunt to the unity post. There shouldbe no deflection. If there is, it is due either to a charge on thecable, which will disappear after a moment, or to earth currents. (Itis assumed that the testing apparatus has been thoroughly tested forinsulation.) If due to earth currents, the conductor is probably apoor one. Earth currents are readily recognizable by their fluctuatingcharacter. Before assuming that the trouble can not be removed, thejoint between the lead and the conductor should be examined again.Moisture on the cable end will give a path for earth currents. Note thevalue and direction of the throw of the galvanometer and record it.

3. Turn the shunt to 0, close the testing key all the way down (+ toearth), noting the time to the second, or starting the stop watch atthe same time, if one is available. The time must be accurately noted.The insulation resistance at the end of one minute’s electrification isthe resistance to be reported.

4. When 35 seconds have elapsed, turn the shunt to the ¹/₁₀₀₀-post andwatch the galvanometer throw; if small, move the shunt successively tothe ¹/₁₀₀-post, to the ¹/₁₀-post, and to the unity post. This operationmust be completed before 45 seconds have elapsed from the time the key[Pg 102]was closed. With good cable the unity post will always be reachedwithout danger of throwing the galvanometer reading off the scale.Remember that each successive post should give 10 times the throw ofthe preceding post.

5. At the end of one minute read the deflection, correct for theleakage of the leads and the earth currents, and record. (See examplefollowing.)

6. At the end of two minutes read the deflection, correct and recordit. For good cable it should be less than the deflection observed atthe end of one minute.

7. Turn the shunt to 0, and reverse the key, stopping at the dischargeposition. Turn the shunt on gradually until the unity post is reachedand wait until the reading is 0, indicating that the conductor isdischarged. If earth currents are present, 0 will not be reachedor will be passed. In this case proceed as before described. Asubmarine mine cable conductor a mile long will discharge ordinarily inabout three minutes.

8. Turn the shunt to 0, stop and start the stop watch; at the same timeclose the key all the way down (- to earth).

9. After 35 seconds, start turning the shunt, ceasing at 45 seconds.(See paragraph 4, above.)

10. At the end of one minute read the deflection, correct and recordit. For good cable it should be substantially the same as thedeflection observed at the end of one minute with + of the battery toearth.

11. Turn the shunt to 0, and reverse the key, stopping at the dischargeposition.

12. Disconnect No. 2 conductor from ground. Disconnect No. 1 from thelead and connect up No. 2. Connect No. 1 to ground. It is not necessaryto wait for No. 1 to be discharged completely before disconnecting it.

13. Proceed with No. 2 as with No. 1 and repeat with each conductor.

14. On the completion of the test all conductor ends should becarefully taped.

15. To determine the correct value of the insulation resistance it is[Pg 103]essential that the negative pole of the battery be connected to thecore of the cable, otherwise the products of electrolysis will tendto seal up any fault which may exist and will cause the conductor toappear better than it really is. With the negative pole of the batteryto the core the tendency is to deposit copper on the core and thusto lay bare any fault. The insulation resistance of any conductor istherefore found by multiplying the corrected deflection at the end ofone minute, with + of battery to earth, by the denominator of the shuntused, and then dividing the galvanometer constant by this product. Theresistance of the ¹/₁₀-megohm box is neglected unless the insulationresistance determined is very low, say, under 1 megohm, when the100,000 ohms should be subtracted from the above quotient.

16. To determine the insulation resistance per mile at 60° F., multiplythe actual insulation resistance found by the length of the cable inmiles, and this result by the multiplier furnished by the torpedo depotfor the particular make of cable, corresponding to the temperature ofthe water in the tank observed during test.

Example.—Leakage of the leads found to be one-half division.Earth currents found to give 1½ divisions in a negative directionfrom 0 of the scale. Galvanometer throw at the end of one minute (+ toearth), 15 divisions. The corrected deflection is, 15 - ½ + 1½ = 16divisions.

The galvanometer constant (450 divisions through ¹/₁₀ megohm, shuntat ¹/₁₀₀₀), 45,000 megohms. That is, the battery will give ¹/₁₀ of450 divisions = 45 through 1 megohm, the shunt at ¹/₁₀₀₀; or, what isthe same thing, one division through 45 megohms, the shunt at ¹/₁₀₀₀;therefore with the shunt at unity the battery will give one divisionthrough 45 × 1,000 = 45,000 megohms. The insulation resistances =45,000 ÷ 16 = 2,813 megohms. If the cable is three-fourths mile long,the insulation resistance in megohms per mile is 2,813 × ¾ = 2,110megohms.

Manufacturer, Safety Insulated Wire & Cable Co.

Temperature of water in tank, 80° F.

[Pg 104]Multiplier, 1.7056; 2,110 × 1.7056 = 3,599 megohms insulationresistance per mile at 60° F. This result is recorded on the form.

VI. Copper resistance.—1. The drop of potential method isquicker than the bridge method under the usual conditions and should beused if the apparatus is available.

Apparatus required.—(a) Source of power (110 volts D.C. lighting circuit, casemate battery or generator); (b) adouble-pole single-throw switch to which the power leads are attached;(c) a bank of ten 110-volt lamps in parallel; (d) a D.C. ammeter of not more than 0-25 scale; (e) a D. C. voltmeter,0-150 scale.

Place the lamp bank and the ammeter in one side of the power line fromthe switch to the conductor, and the other end of the conductor to theother side of the power line. Connect the voltmeter across the endsof the cable so as to measure the drop of potential between the endsof the conductor being tested. Close the switch, take simultaneousreadings on the voltmeter and the ammeter and calculate the resistance.With the apparatus described a conductor 1 mile long will receive about2½ amperes and show a drop of about 50 volts. The lamps are insertedas a safety precaution. In no case should the current through theconductor exceed 6 amperes. If the cable has been tested for insulationresistance and all the conductors show high insulation, the lamps arenot necessary, provided the cable is at least a mile long.

2. The copper resistance found is reduced to that at 60° F. bymultiplying by the coefficient found in the following table with thetemperature of the water in the tank at the time of the test as an argument:[Pg 105]

The true length of a cable should be that of its center conductor.

From the size of the conductor and its copper resistance the length ofthe cable may be computed by use of the following wire table:

[Pg 106]The objections to the use of a bridge for measuring copper resistanceare the difficulty of eliminating the resistance of the plug contactsand the time required to secure balance. The resistance of the plugcontacts may often be as high as 20 ohms, particularly if used at the tank.

If the bridge is used at all, it should be placed in the testing room,and the same leads employed for testing insulation should be used. Theresistance of these leads should first be determined by connectingthem together and measuring; this resistance is subtracted from eachresistance measured.

VII. General.—The key to success in cable testing is greatcare in every detail. The cable now being furnished is all tested withgalvanometers having constants from 200,000 to 250,000 megohms. It hasall been accepted after most careful test. The chances are that itis good when it arrives at the post, unless it has been mechanicallyinjured in transit, which should be ascertained by careful inspectionwhen delivered at the post.

Do not accept a single measurement if it shows low resistance, butrepeat until certain of results. The time between trials on the sameconductor should be as great as practicable. For example: Measurementsshowing low resistance made in the morning should be repeated in theafternoon; those made in the afternoon should be repeated the next day;the conductor being connected to earth during the interval between tests.

Frequent inspections of all articles of submarine mine equipmentshould be made, not only to check up the property, but also todetermine the condition of all matériel, and especially to see if ithas been affected by dampness. These inspections should be thoroughand detailed, as only in this manner can there be impressed on thosedirectly charged with the care of the property the importance ofventilation, dryness, and the proper use of preservatives.

The generating set, storage battery, motor-generators, casematetransformers, power panel, and operating boards will be installed inthe mining casemate, and such tools, appliances, and materials as maybe used when this apparatus is in commission will also be kept there.

The explosive will be kept in the magazines and tested and cared for inthe manner prescribed in Appendix No. 1.

The multiple and single conductor cable will be kept in the cable tanksas described in Appendix No. 4.

All other articles of equipment will ordinarily be kept in thestorehouse, and a noncommissioned officer will be placed directly incharge. It shall be his duty to keep the matériel in the best possiblecondition, using such details from the submarine mine detachment fromtime to time as may be necessary to assist him in this work. He shallcheck up all articles taken from the storehouse during practice andreport at the end of the day’s work any shortage in tools or appliancesthat he may discover.

Paints and oils should be kept separate from other stores, and the floor[Pg 108]where kept should be covered with 2 or 3 inches of sand, to be renewedoccasionally. Sawdust should never be used for this purpose. Cottonwaste which has become unfit for use should be promptly burned. Fusesmust not be stored with other explosives.

Gasoline in considerable quantities should be stored in tanksunderground and never inside of buildings. Small quantities should bekept outside of buildings in some safe place.

When oil engines or generators are out of commission, their brightparts should be covered with light slushing oil. Brass screw threadsand parts of tools that are liable to rust should be covered also. Inall cases the light slushing oil should be applied in a thin coat,since this is all that is necessary to give good protection. Beforeapplying the light slushing oil to any surface it should be thoroughlycleaned, so as to be free from rust, water, kerosene and lubricatingoil, as their presence will cause rusting underneath the slushing oil.The protected surfaces should be occasionally inspected and the coatingof slushing oil renewed as often as required.

Screw threads of mine cases, steel screw threads of compound plugs,bolts, nuts and washers, and surfaces of flat joints should be keptcoated with the light slushing oil or a mixture of machine oil andgraphite.

No oils or grease should ever be placed on points where metalliccontact of electrical instruments is necessary, nor on india rubber,ebonite, or slate.

Mine cases should rest on racks or skids, and where space permitsshould not be in contact with each other. In handling mine casescare must be taken not to damage the bails and bolts. They should bearranged so that the holes in the mine cases can be seen easily; theseholes should be fitted with a wooden plug which has been thoroughlygreased all over its surface. New mine cases, if galvanized, usuallywill not need painting until they have been in the water. When takenfrom the water they should be thoroughly dried, and if they shouldshow signs of rust they should be gone over thoroughly with steel wirebrushes until the rust is removed. Parts which can not be reached withthe brush should be cleaned with three-cornered steel scrapers. A heavy[Pg 109]coat of red lead should then be applied. Seven gallons of this paintcan be made by mixing 100 pounds of red lead ground in oil with 5gallons of raw linseed oil. This mixture should be applied within twoor three weeks after mixing. One gallon of paint should give 10 minecases one coat. After this coat has been allowed to dry there shouldbe applied a coat of white lead toned down to a neutral gray. Sevengallons of this paint can be made by mixing 100 pounds white lead, 2½gallons raw linseed oil, 2½ gallons turpentine, 1 gallon liquid drier,and adding about 1 pound of lampblack to tone down the mixture.

Mines treated in this way, if kept in a dry storehouse, and not put inthe water, should not require repainting for several years. Frequentinspection should be made, however, for in handling the cases andchanging their positions on the racks, it will often happen that anabrasion will be made in the surface of the paint, which if neglectedmay serve as the starting point of a progressive corrosion, which mayextend rapidly under the surface of the paint. Should loose paint orrust be seen the case should be repainted. A small wooden mallet may beused to tap the case at all points to loosen scales of rust or paint;then the surface should be thoroughly wire brushed or scraped and thecases repainted as stated above. The inside of mine cases must beinspected to see that the interior surfaces are kept free from rust.

Ground mines and ground mine buoys should be treated in the manner justdescribed for buoyant mine cases.

If the oil engine has not been painted, it should be given a primingcoat of red lead mixed in oil. This should be rubbed down with pumicestone and two coats of steel-colored paint applied. The second coatshould be rubbed down and two coats of varnish then applied. After thisthe engine should not need repainting for a couple of years. When,however, repainting is necessary, the engine should be rubbed downuntil all the varnish is removed and a coat of steel-colored paintapplied. This coat should be rubbed until no brush marks remain, andone or two coats of varnish should then be applied. The steel-coloredpaint should be applied flat; that is, the color which is ground in[Pg 110]Japan should be mixed with turpentine. One gallon of this paint is morethan sufficient to give an engine two coats.

The motor-generators and the casemate transformers usually will notneed the priming coat of red lead, as they come from the factorypainted. When it is necessary to paint them, one coat of thesteel-colored paint and one of varnish will usually be found sufficient.

Anchors, distribution boxes, junction boxes, mooring sockets, shackles,sister hooks, and the ironwork of operating boards and power panelsshould be painted with asphaltum varnish.

Paint brushes when new, and before use, should be wrapped or bridledwith strong twine and soaked in water to swell. After use they shouldbe cleaned with turpentine and put away in water to keep them fromdrying and becoming unpliable.

Large ropes should be stored on skids, allowing a free circulationof air. Small ropes should be hung on wooden pins. Ropes should beuncoiled semiannually in dry seasons and stretched out for severaldays to dry. Wire rope must be stored in a dry place where it will notrust. Marline-covered wire rope should be stored where there is a faircirculation of air. The date of receipt should be stenciled on eachreel. If not used at the end of five years it should be run througha bath of pure distilled tar oil. This may be done by setting up anempty reel 20 feet in front of the full reel and placing a tub of thetar oil midway between them. As the rope comes off the full reel it ispassed through the oil and the surplus oil slicked off with a pieceof burlap, thus returning the oil to the bath. The freshly oiled reelwill continue to drip for several days, and sand should be put on thefloor under the reel to take up the excess oil. After use in water themarline-covered rope should be thoroughly dried out and then reoiled asabove described.

The matter contained in this appendix is primarily for the informationof the masters of those vessels which are called into service formine planting purposes upon the outbreak or threatening of hostilities.

The master shall request to be supplied with a copy of Regulations forMine Planters, U. S. Army.

To each vessel will be assigned a coast artillery officer, who shallbe the commanding officer of the vessel. All orders for the vesselshall be given to and through him. He shall have general charge of itsbusiness and be responsible for the proper care and disposition ofall stores aboard, leaving to the master of the vessel the full andunquestioned control and authority over all matters for which he isprofessionally responsible.

Any orders to be given by the commanding officer concerning the vesselor its crew will be given to or through the master, except that whenplanting mines or operating any of the mining appliances or machineryaboard the vessel, the commanding officer, or an officer designated byhim, may give instructions directly to any of the vessel’s officers orto members of the vessel’s crew who have duties directly connected withthe mining work.

The duties and responsibilities of the master of a vessel engaged insubmarine mine work do not differ materially from those devolvingupon him when his vessel is otherwise employed. With respect to everyduty the vessel may be called upon to perform, it may be stated thatexplicit directions as to where the vessel is to go and just whatmaneuvers it is to execute in the mine field will be given by the[Pg 112]officer aboard, and it is then incumbent upon the master to execute themaneuver according to his best judgment.

The duties that vessels employed as mine planters are likely to becalled upon to perform are as follows:

• 1. To lay out the mine fields.
• 2. To lay the multiple cable.
• 3. To plant mines.
• 4. To take up mines (including replacing defective
• mines by good ones where necessary).
• 5. To take up the cable.

The commanding officer of the vessel is responsible for the properequipment of the vessel with the necessary apparatus for mine planting,for the loading of all the matériel prior to the planting, and for themethod of procedure under the above heads.

The master of the vessel will carry out the orders of the commandingofficer and is concerned only in the handling of his boat to preventaccidents to it and to the boats engaged in the planting.

The following precautions will be observed by masters:

1. If current flows across the mine field the planting vessel, to avoidaccidents, should always pass on the downstream side of the yawl boatholding the measuring line.

2. The greatest care should be taken that the measuring line and buoyropes are not caught in the propellers. If the vessel has twin screws,the upstream propeller should be stopped as soon as the measuring linehas been passed to the marking boat. In all cases a man with a boathook should be posted near the anchor davits and another amidships, tohold the measuring line above the water and clear of the sides of thevessel. Keg buoys, and as much of the buoy rope as possible, should beheld on the rail near the stern, letting the rope pay out slowly andunder tension, until the propellers are past the rope, then the keg andthe remainder of the rope may be thrown overboard.

3. A general rule is never to back either propeller when buoy ropes,measuring lines, or cables are being handled overboard at or near thestern of the vessel.[Pg 113]

4. If it becomes absolutely necessary to reverse the propellers whenpaying out cable, men paying it out must haul it in taut and keep itabove the wheel and clear of it. The planting vessel should not passnearer than 25 feet to the distribution box boat when cable is leadingout from the latter, nor should it pass over any cable, if it can beavoided, if the depth is less than 16 feet.

5. The vessel should proceed after passing the distribution box boaton such a course that cable will pay off smoothly without becomingentangled. If a cable becomes fouled and entangled, the end shouldbe “let go” at once at the distribution box boat—the planter shouldproceed on, not stop nor back its propellers. Mine cable shouldnever be made fast in the distribution box boat until after a mineis dropped. It is much better to drop the mine out of position thanto endanger the propellers of the vessel. The propeller nearest thedistribution box should be stopped the moment the bow of the vesselpasses the distribution box boat on its course to drop a mine.

6. If, in planting, the vessel moves against the direction ofthe current, there is little danger of overturning the distribution boxboat if ordinary caution is observed. Should it be necessary to plantagainst a cross current or with it, it is best to pass the cable end tothe distribution box boat by a launch or small boat. In this way theplanter need not pass within 50 or 75 yards of the boat.

7. To avoid getting foul of the buoy rope or mine after the mine isdropped, the helm should be put over so as to throw the stern awayfrom the mine. The vessel should be under good headway so that thepropellers may be stopped until they are well past the buoy and buoyropes of the mine. These points are important; failure to observe themwill result disastrously.

In laying multiple cable, the course of the vessel invariably shouldbe against the current. Rather than lay cable with the current it isadvisable to postpone laying the cable until a change of the tidecauses a favorable direction of current. In the end, time will be saved[Pg 114]by waiting. Cable should pay off on the upstream side of thevessel if any cross current is running. All care should be taken thatthe cable does not get caught in the vessel’s propellers. This is ofthe greatest importance.

As the cable pays out over a chock near the bow of the vessel a manshould stand by with a 3-inch strap in readiness to stop the cableshould it be necessary, and two men should manipulate brakes to preventthe cable from paying out too rapidly. This is especially necessary ifthe water is deeper than 50 feet.

Especial care is necessary in planting mines to avoid: (a)Colliding with yawl or distribution box boat; (b) picking upcable in the propeller; (c) getting the mine cable tangled;(d) drifting over the mine after it is dropped.

The left-hand side of a boat or ship, looking toward the bow, is theport side, and the other is the starboard side. The menwho row on the port side are called the port oars and thoserowing on the starboard side are called the starboard oars.

Boats are called single or double banked, according as they have one ortwo oarsmen to a thwart.

Thwarts are the seats on which the crew sits; the space abaftthe after thwart is called the stern sheet.

Floorings and gratings are the bottom boards of a boat.They prevent the weight from bearing directly upon the planking.

The gunwale of a boat is the upper rail.

The yoke is an athwartship piece of wood or metal fitting overthe rudderhead.

Yoke lanyards are the small lines made fast to the ends of theyoke, by which the rudder is turned and the boat steered.

The stem is the upturned portion of the keel at the bow of theboat, to which the forward ends of the planks are secured.

Oars are said to be double banked when two men pull one oar.

The blade of an oar is the broad flattened part. The handle is thesmall part of an oar on the inboard end of the loom, which the oarsmangrasps when pulling. The loom is the portion of an oar extending fromthe blade to the handle. The leather is the portion of an oar whichrests in the rowlock. This is sometimes covered with canvas, but isusually covered with leather; hence the name.

Feathering is the term applied to the operation of turning theblades nearly flat to the water after the stroke, with the upper edgeturned forward, especially valuable in rowing against a head wind.[Pg 116]

Rowlocks are forked pieces of metal in which the leather of theoars rests while pulling. Swivel rowlocks are movable, a pin on therowlock fitting into a socket in the gunwale.

Thole pins are pins set vertically in the gunwale and are usedin place of rowlocks.

The steering rowlock is a peculiar form of swivel rowlock(fitted near the stern of a boat) in which the steering oar is shipped.This is sometimes called a crutch.

The painter is a rope secured in the bow for towing or forsecuring the boat.

Boat-falls are tackles made with two blocks and a length ofrope; used for hoisting boats.

The plug is the wooden stopper fitted into a hole in the bottomof a boat to let water in or out.

A boat breaker is a small keg used for carrying fresh water.

A boat-recall is an understood signal made to order a boat’sreturn.

BOAT ORDERS.

Oars and rowlocks having been placed in the boat, blades of oarstoward the bow, rudder and yoke, if any, stepped and the yoke lanyardsclear, the men board and take their proper seats. The man pulling thebow-oar is No. 1, the next man is No. 2, and so on, to the man pullingthe stern-oar, who is called the “stroke-oar.” The men being seated,with oars handy, the bow-man, who may be No. 1 or an extra man, asconvenient, holds onto the wharf, side, or piling, as the case may be,with his boat hook.

Shove off.—At this command the bow-man shoves the boat clear,giving her headway if possible. He boats his boat hook and takes hisseat.

Up oars.—The crew simultaneously seize and raise their oarssmartly to the vertical (guiding on the stroke-oar) and hold themdirectly in front of them, the blades fore-and-aft, inboard handsgrasping the handles, holding the same well down between the knees,outboard hands grasping the looms at the height of the chin.

Let fall.—The oars are eased down into the rowlocks together,[Pg 117]brought level with the gunwale, blades horizontal and all trimmed onthe after oars. Oars must not be allowed to splash.

(1) Give way together, (2) GIVE WAY.

At the first command the men reach well forward, blades nearlyvertical, ready for the stroke. At the second command they dip theiroars at the same time as the stroke-oar and commence rowing, keepingstroke exactly and all lifting their blades to the height of thegunwale on the return. (Or higher if waves render this necessary.)

TO MAKE A LANDING.

In running alongside a vessel or up to a float-stage or wharf, whenseveral lengths away from same, give the command (while the oars arein the water), IN BOWS. The bow oarsman (if there be no extraman in the bow) finishes his stroke, then “tosses” and “boats” his oar,blade to the bow, and stands ready with the boat hook to fend off andhold the landing. When there is sufficient headway to carry the boatproperly to the landing, give the command, WAY ENOUGH. Thisorder is given while the oars are in the water; the men finish thestroke, then toss and boat their oars with as little noise as possible.The oars are next the rail, the after oars outboard of the bow oars.If the stroke oarsman is provided with a boat hook, he grasps it andstands ready to help the bow man.

If it be desired to stop rowing temporarily, give the preparatorycommand, (1) Stand by to lay on oars, at which the crew paysstrict attention. Then, when ready, give (2) OARS. At thiscommand, given while the oars are in the water, the crew finishes thestroke and brings the oars level with the gunwale, blades horizontal,trimmed on the after oars. This position is also used for salutes, asnoted hereafter.

If about to pass so close to another boat that a collision of oarsseems probable, command (1) Trail, (2) OARS. At thesecond command, given while the oars are in the water, the men finishthe stroke, and then, while the oars are still in the water, by lifting[Pg 118]the handles with their outboard hands the looms are thrown out of therowlocks. The men carry their hands outboard till the backs of theirwrists rest on the rails and the oars trail astern. (This movementis used in shooting bridges, where lack of head room precludes tossing.)

To bring the oars inboard, command: OARS.

At this command the men raise the handles, lower the looms intothe rowlocks, and then raise the blades out of the water and swing theoars to the regular position of Let fall.

In order to turn the boat short around (being stationary or nearly so)command: (1) Give way, starboard; back port, (2) GIVEWAY; or (1) Give way, port; back, starboard,(2) GIVE WAY. The crew keeps stroke just as regularly as inpulling straight away. As soon as the boat points in the desireddirection command: (1) Give way together, (2) GIVE WAY.

If it be desired to check the boat’s headway, command: HOLDWATER. At this command the men drop their blades vertically intothe water, tops of blades inclined slightly forward, inboard handsgrasping the handles, outboard arms over the looms to steady the oarsagainst the chest. To prepare the crew for rowing command OARS,at which they resume the position described under the heading Letfall.

To move the boat astern command STERN ALL.

At this command the men back water, keeping stroke as regularly as inordinary rowing. To resume the position of attention give the commandOARS, as before.

To toss oars command: (1) Stand by to toss, (2) TOSS.

The command of execution is given while the oars are in the water,the stroke is completed and the oars raised smartly to the vertical,with blades in fore-and-aft plane, handles of oars on bottom boards,the wrists of the inboard hands resting on the thighs, outboard handsgrasping the looms at the height of the chin, crew sitting upright. Toplace the oars in the boat give the command BOAT YOUR OARS. Atthis command the oars are lowered toward the bow (not swung outboard)and laid in the boat as before described. This command may be givenfrom the position of Let fall, in which case the men toss theiroars and proceed as above.[Pg 119]

NOTES.

In rowing the blade of the oar should be raised as high as the gunwaleafter leaving the water and feathered by dropping the wrist. A barelyperceptible pause should be made, and the oar next thrown well forwardand dropped edgewise into the water, taking care to avoid splashing andchopping. Now swing the oar smartly through the water without giving itany final jerk, and repeat as above. With green crews it may be foundnecessary for the coxswain to call stroke, stroke, in order toget the men to pull exactly together.

There should be a mark on the loom of the oar (about the height ofthe eyes when the oar is at toss) to show when the blade isfore-and-aft, thus avoiding the necessity of the men gazing up for thepurpose of finding out when this is the case. Never allow a boat’s crewto splash with the blades when executing Let fall. When restingon oars, insist that they be kept level with the gunwale and at rightangles to the keel. Talking among the crew and turning the heads tolook at any object should never be allowed while the boat is underway. In most cases, boats should be permanently equipped with a smallbreaker of fresh water, a spare oar and oarlock and a suitable anchoror grapnel. The anchor rope to withstand a storm should be six (6)times as long as the greatest depth liable to be used as an anchorage.For any small boat in our service a 20-pound anchor and 12-thread(about 1 inch) manila hawser should easily weather a hurricane. A boatshould never go out at night without a good, well-filled lantern. Manya boat has been run down through its inability to make its presenceknown. Before leaving the shore in foggy weather, provide the boatwith some sort of a foghorn and a compass, and calculate as nearlyas possible the bearings of the landing you wish to make. Take theopposite of this upon returning, making due allowance for tide and windin both cases. To ride out a gale of wind in an open boat, lash theoars and grating together, making them into a bulky bundle and weightthem if possible; span them with the painter and pitch them overboard.This will keep the boat’s head to the sea and prevent her from driftingfast. Assist the boat to take the seas head-on by means of a steering[Pg 120]oar. In rowing through a chop, where the rudder is apt to be pitchedclear of the water, it should be unshipped and a steering oar usedinstead. Remember, in making a landing, that the heavier the boat isladen the longer she will keep her way. If you are being towed by asteamer, make her give you a line, instead of using your own, and belayit so it can be cast off in a hurry. Carefully avoid weighing downthe bow; always use a short towline when the boat is empty and a longtowline when the boat is laden. If the boat’s painter is used for atowline, have a knife ready for cutting it if it becomes necessary.Never go close under a steamer’s stern unless it is absolutely unavoidable.

Officers in boarding a ship, use the starboard gangway, although theymay use the port gangway. Enlisted men use the port gangway or thebooms, unless otherwise ordered.

Boat salutes.—The following salutes should be exchanged betweenboats meeting or passing each other. No junior should pass ahead of asenior without permission.

The junior should always salute first, and the senior should return thesalute by touching his cap.

Salutes should be exchanged whenever boats pass near enough to eachother for the senior officer to be recognized, whether he be in uniformor not.

Officers without a flag or pennant flying should be saluted with thehand only; those with a flag or pennant flying should, in addition, besaluted by laying on oars.

When a noncommissioned officer is in a boat and meets another boatcontaining an officer he stands and salutes. If the boat flies a flagor pennant, the noncommissioned officer, in addition, lays on oars.

Officers of the Navy and Marine Corps and foreign officers in boatsshould always be saluted when recognized.

In laden boats, towing boats, or boats under sail the hand salute onlyis made on all occasions.

Coxswains in charge of boats shall always rise and salute when officersenter or leave their boats.

Boat keepers shall stand up and salute officers passing in boats andremain standing until the boat has come alongside or passed.

• APPARATUS.
• Ammeters, portable, 0-25 scale, 1 to each post.
• Anchors, buoy, 500 pounds, 5 to each group of 19 mines.
• Anchors, mine, 1 to each buoyant mine.
• Axle, cable-reel, 1 to each cable-reel frame.
• Balances and weights, 1 set to each post.
• Battery, storage, 1 to each casemate.
• Boards, operating, 1 to each group of 19 mines.
• Boxes, distribution, 1 to each group of 19 mines.
• Boxes, distribution, 1 to each group of 7 mines.
• Boxes, junction, large, 3 to each mile of multiple cable.
• Boxes, junction, small, 1 to each mile of single-conductor cable.
• Buoy, distribution box, 1 to each distribution box.
• Buoy, marking, 5 to each group of 19 mines.
• Buoy, mine, 1 to each buoyant mine.
• Cable, submarine, 19-conductor, according to project.
• Cable, submarine, 7-conductor, according to project.
• Cable, submarine, 1 conductor, according to project.
• Cases, guncotton, as required.
• Circuit closer, 1 to each mine transformer.
• Clips, cable, 2 for each mine.
• Engine, internal combustion, 1 to each casemate.
• Frame, cable-reel, 3 to each post.
• Fuse can, 1 to each compound plug.
• Generator, casemate, 1 to each casemate.
• Mine cases, according to project.
• Motor generator, D. C.-A. C., 2 to each casemate.
• Panels, power, 1 to each casemate.
• Planting equipment for emergency vessels, 1 to each vessel:
• Each planting equipment consists of—
• 1 axle, cable-reel.
• 4 blocks, snatch.
• 4 blocks, triplex, 2-ton.
• 2 come-alongs.
• 2 davits, anchor.
• 2 davits, mine.
• 1 frame, cable-reel.
• 4 hooks, trip. [Pg 122]
• Plugs, compound, 1 to each mine case.
• Reels, cable, according to cable on hand.
• Reel and frame, measuring, 1 to each mine field.
• Shackles, anchor, 2 to each anchor.
• Shackles, mine, 2 to each mine.
• Sister hooks, 1 pair to each anchor.
• Sockets, mooring, 2 to each buoyant mine, for wire rope only.
• Springs, automatic anchor, 6 extra for each group of 19 mines.
• Switches, starting, 1 to each motor generator, D. C.-A. C.
• Telephones, boat, 4 to each mine field.
• Testing set, insulation, 1 to each post having a cable tank:
• Each testing set consists of—
• 1 box, resistance, 100,000 ohms.
• 2 cases for instruments.
• 1 galvanometer, D’Arsonval, reflecting.
• 1 key, special insulation testing.
• 1 repair kit.
• 1 shunt, Ayrton Universal.
• Transformer, casemate, 2 to each casemate.
• Transformer, mine, 1 to each mine.
• Voltmeter, portable, 0-3-volt scale, 1 to each storage battery.
• Voltmeter, portable, 0-150-volt scale, 2 to each post.
• Weights, distance, for automatic anchor, 6 extra for each
• group of 19 mines.

• UTENSILS.
• (Supply for each post, unless otherwise indicated.)
• 1 anvil, 50-pound.
• 3 axes, handled.
• 6 basins, wash.
• 24 binding posts (to each casemate).
• 2 blocks, tackle, double.
• 2 blocks, tackle, single.
• 6 boxes, tool.
• 6 brushes, battery.
• 6 brushes, dust.
• 6 brushes, paint, flat.
• 6 brushes, paint, oval.
• 12 brushes, sash.
• 12 brushes, scratch.
• 6 buckets, galvanized iron.
• 1 chest, carpenter’s tool:
• The chest contains the following tools—
• 1 bits, set, of 13.
• 1 bit, expansive,
• 1 brace, ratchet. [Pg 123]
• 1 chisels, carpenter’s, set of 6.
• 1 hammer, claw.
• 1 knife, drawing.
• 1 level, carpenter’s.
• 1 oilstone.
• 1 plane, jack.
• 1 plane, smooth.
• 1 rule, 2-foot.
• 1 saw, compass.
• 1 saw, hand.
• 1 saw, rip.
• 1 saw set.
• 1 square, carpenter’s.
• 6 chisels, cold.
• 4 clips, wire rope (for each buoyant mine).
• 4 coppers, soldering.
• 3 crowbars.
• 6 cups, drinking.
• 2 cutters, cable.
• 1 dies, letters, set.
• 1 dies, numbers, set.
• 1 drill, breast.
• 1 drill points, set of 15.
• 6 files, 6-inch, flat bastard.
• 3 files, 6-inch, slim taper.
• 6 funnels, loading, large.
• 6 funnels, loading, small.
• 1 gloves, rubber, pair (to each storage battery).
• 1 grindstone.
• 24 hacksaw blades.
• 4 hacksaw frames.
• 6 hammers, ball peen.
• 6 hammers, smith’s.
• 2 handles, with tools.
• 3 hatchets.
• 6 hooks, boat.
• 2 hydrometers, battery (to each storage battery).
• 3 irons, calking.
• 4 irons, grappling.
• 120 knives, submarine mine (for each mine company,
• to be issued as part of equipment).
• 3 ladles.
• 6 lamps, alcohol.
• 2 lamps, battery inspection (to each storage battery).
• 3 lamps, Khotal. [Pg 124]
• 5 leads, sounding.
• 12 levers for socket wrenches.
• 12 life buoys.
• 12 life preservers.
• 2 mallets, large.
• 2 mallets, small.
• 12 marlinespikes.
• 6 megaphones.
• 1 oilers and tray, set (to each casemate).
• 12 padlocks, brass, with chain.
• 2 pitchers, acid (to each storage battery).
• 2 plates, earth.
• 70 pliers, side cutting, 5½ inch
• (for each mine company, to be issued as part of equipment).
• 50 pliers, side cutting, 8-inch
• (for each mine company, to be issued as part of equipment).
• 3 pots, melting.
• 4 pumps, boat (to each mine field).
• 2 scales, extension spring, reading 200 pounds.
• 1 scales, portable platform.
• 6 scissors, 8-inch.
• 6 scoops, large, for trotol only.
• 6 scoops, small, for trotol only.
• 12 scrapers, iron, with handle.
• 4 screw-drivers, large.
• 4 screw-drivers, medium.
• 4 screw-drivers, small.
• 6 switches, assorted (to each casemate).
• 2 syringes, battery (to each storage battery).
• 3 tapes, measuring.
• 2 thermometers, battery (to each storage battery).
• 2 thermometers, cable tank.
• 2 thimbles, galvanized iron (to each buoyant mine case).
• 2 tongs, cable-reel.
• 6 torches, gasoline, hand.
• 2 trucks, mine case.
• 6 vises, bench, large.
• 6 wrenches, monkey, 8-inch.
• 6 wrenches, monkey, 15-inch.
• 12 wrenches, S.
• 6 wrenches, socket.
• 6 wrenches, spanner.
• 3 wrenches, Stillson.
• 6 wrenches, T, small.

• EXPENDABLE STORES.[Pg 125]
• Alcohol, wood, 5 gallons to each post.
• Antimony for socket alloy, 10 pounds to each 19 mines.
• Books, record of cable test, 1 to each post.
• Books, daily test, 2 to each post.
• Books, note, 24 to each post.
• Brushes, carbon, 4 extra for each machine requiring them.
• Brushes, wire, 4 extra for each machine requiring them.
• Cells, dry, large, 25 to each post.
• Cells, dry, small, 100 to each post.
• Cement, rubber, 3 pounds to each 19 mines.
• Cleats, porcelain, 1-wire, 50 to each casemate.
• Cleats, porcelain, 2-wire, 50 to each casemate.
• Collars, Turk’s-head, large, 10 to each mile of 7-conductor cable.
• Collars, Turk’s-head, medium, 10 to each mile of 19-conductor cable.
• Collars, Turk’s-head, small, 5 to each mine.
• Compound, commutator, 1 stick to each casemate.
• Connectors, double, 25 to each casemate.
• Cords, telephone, 4 extra.
• Crayons, marking, 12 to each storehouse.
• Cut-outs, porcelain, 2 to each casemate.
• Drier, as required.
• Electrolyte, specific gravity 1210, 4 carboys to each casemate.
• Explosive, according to project.
• Fuses, service, 4 to each mine.
• Gasoline, for torches, 10 gallons to each post.
• Glands for compound plugs, 2 extra for each plug.
• Glue, 5 pounds to each post.
• Graphite, as required.
• Handles, assorted, as required for repairing tools.
• Insulators, glass, 25 to each storehouse.
• Jointers, copper, 1 pound to each 19 mines.
• Keys, distribution box, flat, 4 extra to each box.
• Keys, distribution box, split, 4 extra to each box.
• Keys, mine case, 2 extra for each mine case.
• Keys, shackle, 1 extra to each shackle.
• Knobs, porcelain, 100 to each post.
• Lampblack, 2 pounds to each 100 pounds of white lead.
• Lamps, incandescent, white, 110 volts, 16-candlepower,
• 12 to each casemate.
• Lamps, incandescent, white, 80 volts, 16-candlepower,
• 12 to each casemate.
• Lamps, incandescent, red, 80 volts, 8-candlepower,
• 3 to each operating board.
• Lamps, incandescent, green, 45 volts, 8-candlepower,
• 3 to each operating board.
• Lamps, incandescent, green, 45 volts, 16-candlepower,
• 3 to each operating board.
• Lamps, incandescent, green, 45 volts, 32-candlepower,
• 3 to each operatingboard. [Pg 126]
• Lead, for socket alloy, 90 pounds for each 19 mines.
• Lead, red, as required.
• Lead, white, as required.
• Line, cod, 2,000 feet to each post.
• Line, measuring, 2,000 feet to each post.
• Line, sounding, 500 feet to each post.
• Lye, as required.
• Marline, 1 pound to each mine.
• Nails, assorted sizes, 25 pounds to each post.
• Needles, cleaning, for Khotal lamps, 6 to each post.
• Nipples, soft rubber, 1 to each hard rubber fuse can.
• Oakum, 50 pounds to each post.
• Oil, cylinder, 5 gallons to each casemate.
• Oil, dynamo, 1 gallon to each casemate.
• Oil, lubricating, 1 gallon to each storehouse.
• Oil, linseed, as required, 3 gallons to 100 pounds of lead.
• Oil, slushing, 5 gallons to each post.
• Oil, tar, as required for marline-covered rope.
• Oil, transformer, 1 gallon to each casemate transformer.
• Packing, asbestos sheet, 2 pounds to each casemate.
• Packing, asbestos wick, 1 pound to each casemate.
• Packings, rubber, 100 to each 19 mines.
• Paint, acid-resisting, as required.
• Paint, steel color, for casemate apparatus, as required.
• Paste, soldering, 1 pound to each post.
• Paraffin, 10 pounds to each post.
• Pencils, lead, 6 dozen to each post.
• Plugs, attachment, 6 to each post.
• Pomade, Putz, 3 pounds to each post.
• Primers, explosive, 1 to each mine charge.
• Pumice stone, 2 pounds to each casemate.
• Resin, 2 pounds to each post.
• Rope, for distance weight, 20 feet for each automatic anchor.
• Rope for heaving lines, 1,200 feet to each post.
• Rope for lashings, 1,200 feet to each post.
• Rope, marline-covered, according to project.
• Rope, raising, 50 per cent more than of mooring rope.
• Rope, wire mooring, according to project.
• Rosettes, 24 to each post.
• Ruberine, 5 gallons to each post.
• Sandpaper, 48 sheets to each post.
• Sapolio, 10 cakes to each post.
• Screws, brass, assorted sizes, 1 gross when required.
• Screws, iron, assorted sizes, 1 gross when required.
• Screws, set, for compound plugs, 1 extra set for each compound plug.
• Screws, set, for mine transformers, 1 extra set
• for each mine transformer. [Pg 127]
• Shellac for insulation purposes, 5 pounds to each post.
• Soap, 25 cakes to each post.
• Sockets, lamp, 12 to each casemate.
• Solder, wire, 5 pounds to each post.
• Staples, large, 20 pounds to each post.
• Staples, small, 1 pound to each post.
• Suspensions, galvanometer, lower, 3 to each insulation testing set.
• Suspensions, galvanometer, upper, 6 to each insulation testing set.
• Tags, brass, 50 per group of 19 mines.
• Tags, lead, 50 per group of 19 mines.
• Tags, linen, 50 per group of 19 mines.
• Tape, protective, 5 pounds to each 19 mines.
• Tape, rubber, 5 pounds to each 19 mines.
• Tinfoil, 1 pound to each 19 mines.
• Towelling, 10 yards to each post.
• Tubes, porcelain, 12 to each post.
• Turpentine, as required.
• Twine, 3 pounds to each 19 mines.
• Varnish, asphaltum, as required.
• Varnish, spar, as required.
• Washers, brass, 100 to each 19 mines.
• Washers, lead, 1 extra set for each compound plug.
• Waste, cotton, 50 pounds to each post.
• Wire, casemate, extra, 100 feet each of black, blue, red, and brown
• to each casemate.
• Wire, fuse, 1 pound each of 3, 12, and 25 ampere to each casemate.
• Wire, lamp-cord, extra 100 feet to each casemate.
• Wire, loading, 20 feet to each mine.
• Wire, soft-drawn copper.

Remarks: