replaced in proper position. The form of cell and arrangement of the different parts will be understood from Fig. 25.

Fig. 26 shows an adaptation of the Marie Davy cell to field-use. The containing vessel is of ebonite and the cover screws on water-tight. The zinc is kept in place by studs that fit closely into the containing-cell, and into one of which a screw-post passes from the outside. The porous cup is'of leather and is fastened to the cover. The negative element is carbon, a plug of which is fitted with a metallic head that screws into the cover within the porous cup. This cell is charged by filling the porous cup with a paste of the bisulphate of mercury and water and the outer cell with the water in which the paste was made. The action is similar to that of the copper

zinc pair, the oxygen of

the water attacking the zinc and the freed hydrogen finding its office in reducing the mercury from its crystalline salt. It gives off no gas and works as long as any of the salt remains in the porous cup.

In the absence of any form of battery especially adapted for field use, any of those described herein can of course be used, and the ingenuity of the officer must be his reliance. The principal difficulty will be found in providing transportation for them, and this must be overcome in the best possible manner. The signal-service battery can be made roughly under almost any circumstances-out of a feedtrough, by putting in partitions and coating the inside with wax, tallow, pitch, or other nonconductor; out of a number of buckets, or, in brief, any vessel that will hold the elements. Cotton, tow, sawdust, spent tanbark, sand, or almost any porous substance may be substituted for the sponge, and the battery be made to answer a good purpose until others can be procured. The white vitriol is not indispensable, as the battery will work without it, only requiring a few hours' time to come to its full strength.

Fig. 26.

The ground-connections for a field-line are necessarily such as can be quickly made and easily removed. The most convenient form is that of a cylindrical iron bar, 5 feet long and 1 inch in diameter, pointed at one end and fitted at the other with a binding-screw by which to attach the ground-wire, the whole zinc-coated, (galvanized,) to prevent oxidation and to present always a bright surface to the earth. Such a bar, driven two-thirds of its length into moist earth, is a sufficient ground-connection for field-lines of thirty miles in length. In cases where the earth at the station is so dry as to render the bar ineffectual, moist earth must be sought at a distance and the ground-wire run to it, or the earth moistened by pouring water into the hole made by the bar, the first-named method being preferable for the reason that the moisture in the second case will scarcely be carried far enough to remedy

the defect.

Ground-connections may be made as for permanent lines whenever circumstances (loss of

bars, &c.) may render it necessary or convenient to do so. The rule to be followed is the same in one case as in the other-a surface in contact with earth that shall equal in conductivity the battery and line.

The tools for the erection of a field-line (which constitute, with the materials for the line, the outfit of the train) are: marking-pins, by which the points of support are indicated; axes and hatchets, to cut away shrubs or branches of trees or to affix insulators to natural supports; crow-bars, to make holes in the earth in which to set the lances; bars, fitted for cutting through frozen ground; climbers, to enable the men engaged in the work to ascend trees, when necessary, for the purpose of affixing insulators thereto, or to trim away branches; reels, for the delivery and recovery (uncoiling and recoiling) of the wire; pliers, to be used in making connections: files and screw-connectors, which are to be used for making connec tions between the coils (mile-lengths) of wire in reeling out, and generally where connec tions are to be frequently made and broken, to avoid loss of time and waste of wire.

The marking-pins are of iron wire, one-eighth inch in diameter and 15 inches long, pointed at one end and having a loop or handle at the other, painted of some bright color. and fitted with a small pennon of bright-colored cloth, so as to be conspicuous objects, and are used to mark the places where lances are to be erected, by being thrust into the earth at such points, or the natural supports to which insulators should be affixed by the same methods.

It is scarcely necessary to describe axes or batchets, except, perhaps, to say that the latter should have a hammer-poll with which to drive a spike. But the efficiency of the line may depend on their use, which is mainly to cut down all shrubs growing near the line-wire, to trim off such as come, or might be thrown by the wind, in contact with the line-wire.

Crow-bars, with which to make seats for the lances, are cylindrical iron bars 4 feet long, 1 inches in diameter for 2 feet from the point, and 1 inch in diameter for the rest of their length, and pointed so as to penetrate the earth easily. Such a bar weighs fifteen pounds. These (and all the iron used in the work) should be zinc-coated, (galvanized.)

Ice-bars are of the same general form and dimensions as the crow-bars, but have a wide chisel-shaped point or blade, and are used for cutting through frozen ground, to facilitate the work of setting the lances.

Climbers, to enable the men engaged in erecting a line to ascend trees to affix insulators and attach the wire, are of various patterns. A good form is made of steel, with leathern straps for attaching them to the feet, and weigh about four pounds the pair. A strap of sling is carried over the shoulder of the man and used to aid him in maintaining his posi tion without the use of his hands, leaving them free for the work of handling his tools.

Reels for field use are in general form like those for permanent lines, but are lighter, and are provided with arms attached to the uprights, which are laid flush with the face of the uprights when reeling out wire, and secured at right-angles there to when reeling up, in order to confine the wire and give the coil its proper shape. Each one has a handle affixed to the extremity of one of the upper cross-armis, by which it is turned when reeling up wire. The reel is seated in the wire-wagon, but may be carried by men over ground impractica ble for the wagons in the hand-bearer, one of which should accompany each reel.

Pliers and files are of the same kinds as for permanent lines, but smaller, as the wire is smaller and the work to be done lighter. Connectors are simply brass cylinders, perforated through their length to admit the wires, and fitted with a thumb-screw, the end of which presses upon and holds the wires so inserted.

CHAPTER VIII.

The vehicles used for the transportation of the materials, tools, and equipments are also used for offices or stations, and are called battery-wagons, wire-wagons, and lance-trucks. The battery-wagon is the central or headquarters office; is of a size sufficient to contain four instrument tables, the necessary batteries for four lines, each ten miles in length, instru ments and table apparatus for each table, four ground-bars, a supply of battery-material, seats for four operators, and a stove.

It is mounted on platform-springs, and turns in its own length, is covered with canvas, and must not be too heavy to be drawn by two horses over any ground practicable for artillery. The tables are each 24 feet long by 1 foot or 1 foot 3 three inches wide; are attached to the sides of the wagon at a height from the floor of 24 feet; one in each corner of the wagon. The batteries, in sections or cases of six cells each, are supported by brackets underneath the tables, each bracket being of a size sufficient to support two such sections. The instru ments and table-apparatus are carried, when not in use, in pouches of leather attached to the sides of the wagon between the tables; the supply of battery-material in a box under neath the driver's seat; the ground-bars on the floor, next the sides, (two on each side,) and confined by clamps and keys; and the seats for the operators (camp-stools) in any con venient manner. The stove is placed in the center of the floor and secured against displacement. The wagon is entered by a door at the rear.

The wire-wagon is of the same general form as the battery-wagon, and mounted in the same manner. It is of size and strength to contain an instrument-table, which is attached to the front end; a single section of battery underneath the table; a pouch for instrument and apparatus at its side; a seat (camp-stool) for the operator; a ground-bar, secured as in the battery-wagon; a wire-reel, seated in a socket in the center of the floor near the hind end; a hand-bearer, secured at the top of the wagon by straps; ten coils of wire, (one mile in each,) secured for transportation at the sides of the wagon; and a box, which serves to hold the wireman's tools (pliers, files, and connectors) and as a seat for him when at work reeling out or recovering wire. This wagon must be strong to safely carry its load, but must at the same time be light enough to be handled by two horses on roads or ordinary ground, and by four over any ground at all practicable for wagons.

The lance-truck is a wagon without springs, of length sufficient to carry lances, and of strength sufficient to sustain the weight of 250 lances and all the line-tools and insulators for ten miles of line. The lances are stowed compactly in the middle of the wagon or truck and confined by upright stanchions and end-boards. The insulators and tools are contained in boxes arranged for the purpose on either side of the pile of lances. The weight of the load will be approximately 3,000 pounds, and a good six-mule team will be needed to move it. It carries 250 lances, 400 insulators, 16 crow-bars, 4 ice-bars, 2 axes, 12 hatchets, 12 pairs of climbers, and 80 or more marking-pins.

A full train consists of one battery-wagon, four wire-wagons, and four lance-trucks, and is divided into four sections, each of which consists of a wire-wagon and lance-truck and is capable of acting independently. Thus a full train may erect lines radiating in four directions from the battery-wagon; or the four sections, the second commencing to reel out its wire when the first has finished, may extend a single line forty miles long, having offices at the termini and at three intermediate points equidistant from each other. Additional instruments being furnished, intermediate offices other than the regular ones can be opened when

ever necessary.

The train is commanded by a chief of train, whose place is with or near the headquarters of the force with which the train is acting, and with him the battery-wagon with its complement of operators, battery-man, and driver. To work the four lines separately twelve operators will be the ordinary number, three for each of the lines, giving to each eight hours' duty out of each twenty-four; and this should be divided into two tours or watches of four hours each. Should the work to be done by the lines be exceedingly heavy, this force might be increased to advantage, and under other circumstances might perhaps be reduced; but it is false economy to require too much of men, and eight hours of close attention is fully enough. The battery-man will have charge of and be held responsible for the batteries, not only those in the battery-wagon but also those in the wire-wagons; will see that they are at all times in order and ready for work; have the care of the supplies for them, and make regular reports to the chief of train, embracing all necessary information concerning them. Each section will be commanded by a chief of section and manned by four non-commissioned officers and thirty-six men, whose several duties will be as follows:

One director, (non-commissioned officer,) who, receiving from the chief of section general orders concerning the direction to be taken or point to be reached, will go over the ground and select the route for the line. He will be accompanied by two markers carrying guidons, whom he will station so as to guide the surveyor. The director should be carefully selected, as upon his skill and judgment depends, in a great degree, the promptness with which lines can be erected. He must take the most direct line practicable to the point he has to reach, but, in order to determine what is best, he must examine the character of the ground and know that there are no obstacles insuperable to the train-streams, ravines, bluffs, or marshes; that the soil is such that the line can be erected-not loose sand or rocks; that the route he selects is not made impracticable by the guns of an enemy; and, in short, must bear in mind all the contingencies to which the train or line may be subjected, and be governed by the circumstances of the case. The director and markers must be mounted, and each marker, on being relieved from post by the arrival of the surveyor, will rejoin the director. Over difficult ground it may be necessary to increase the number of markers, and upon a road or over country well known it may be practicable to dispense with them entirely, the director accompanying or slightly preceding the surveyor. For night-work the markers will carry a lantern instead of a guidon.

One surveyor, whose duty it is to move toward the marker in sight, measuring the distance by paces and directing the pin-men where to plant the marking-pins. He will be governed by the general rules for locating lines as laid down herein, in which he should be thoroughly instructed. He is accompanied by three pin-men, two of whom have each forty or more marking-pins, which they plant at points indicated by the surveyor, to indicate the place where lances are to be erected, or insulators attached, if natural supports are used. The first man, when his pins are expended, halts until the third, who follows the lance-men, has gathered the pins and overtaken him, when he rejoins the surveyor, and the second on expending his pins does the same, the first and second relieving each other and the third bringing up the pins when the line is erected.

Thirteen bar-men, twelve of whom are equipped with a crow-bar, with which, at the points indicated by the marking-pins, they make holes for the foot of the lances. This must

be carefully done, and that it is so it is the duty of the thirteenth, who is a non-commissioned officer and chief of the detachment, to see. The holes must be fully 2 feet deep, which will be the case if the shoulder of the bar is below the surface when the point is at the bottom of the hole, and large enough to admit the lance easily. As the lance is of twice the diameter of the bar, the hole must be made of the proper size by working the bar around and pressing back the earth, and this should be done as the bar is driven down, for if the bar be driven first to the full depth and then worked, it will be difficult to sufficiently enlarge the hole in ordinary soils, and when done will not be of uniform size, but large at top and bottom, and smaller midway, a point to be avoided, as in such a hole the lance will be easily drawn from a perpendicular even if it can be forced to the bottom. The bar-man, standing erect, should grasp his bar near the top with both hands and drive it into the ground, working with hands close together, as, if he grasps the bar with one hand near the top and the other below, he will not work as easily or direct the blows of the bar so accurately, but will be compelled to bend his body sidewise, his upper hand will throw the top of the bar from him and the lower hand draw the point toward him; the work will be done in a slovenly manner, and the hole when completed not be perpendicular.

Two wire-men, whose duties are to accompany the wire-wagon and attend to the reeling out and reeling up of the wire. They will, in reeling out, place the coils of wire upon the reel, remove the straps or wires by which it is bound, and one of them, seated in the wagon, by the use of the brake so control the motion of the reel that the wire shall be laid straight and without slack, and will make the necessary connections as the coils are one after another paid out. Joints in field-wire should be made in the same manner as in wire for permanent lines, except that to join the end of one coil to that of another it is well to use a wire-connector, as these joints mark off the line into mile-lengths for convenience in recovering the line and recoiling the wire, and time is saved by their use. All joints other than these must be carefully made in the same manner as for permanent lines, and soldered The second man will follow the wagon and carry the wire to the line of lances, and render such assistance to the first as may be required.

Thirteen lance-men (one of the number being a non-commissioned officer and chief of the detachment) will affix the insulators to the lances and deliver a lance and insulator at each hole, one or two men being mounted upon the lance-truck for that purpose, and the others will place the wire in the insulators, erect the lance, thrust its foot into the hole prepared for it by the bar-men, and stamp the earth solidly around it.

Three operators, to work the station when opened, and drivers for the wire-wagon and lance-truck, complete the force.

CHAPTER IX.

TRAIN DRILL-(ONE SECTION.)

The minimum force for illustrative drills with a section-train is as follows: One (1) liet tenant, one (1) director, one (1) surveyor, two (2) pin-men, seven (7) bar-men, two wire-men, seven (7) lance-men, two (2) operators, and three (3) drivers.

It will be parked in the following order:

Wire-wagon in line with and ten (10) paces on the left of the battery-wagon, and the lance-truck in rear of the center of the wagons, with distance of ten (10) paces, as indiestei in Fig. 27.* The figures refer to the illustrations of the train-drill given in the manual. At the "first call" the drivers, director, and markers will saddle and harness up. When the assembly" is sounded the drivers will lead out and hitch up, the director and markers will lead out and take position immediately in front of the train, and with the drivers will stand at "attention" and "dismounted." The drivers, when dismounted, will always stand at their horses' heads.

The men for duty with the section will be formed on the parade in two ranks, the rel called, and the detachments told off, the latter taking position in the following order: Ite surveyor and pin-men on the right, the bar-men with an interval of two paces, the wire-men with an interval of two paces, the lance-men with an interval of two paces, the operators and battery-men with the same interval.

They will be marched in column of detachments to the ground where the train is parked and wheeled into line by the flank previously designated, facing the train.

The section-train being in park, with the detachments in line near it, the chief of train wishing to form the train in column of route, will command

1. "Form train front, (right, left, or rear.")

2. " March, (or double time, march.")

The train is always formed on the line of direction of the battery-wagon, whether the train be in disorder or in park.

At the first command the director, markers, and drivers mount, and director and markers

*The figures refer to the illustrations of the train-drill given in the manual of signals.

and battery-wagon move, if necessary, to take the direction indicated. The chiefs of detachments give the cautionary commands to cause their detachments to move toward the proposed front. At the second command the battery-wagon halts, the director and markers take post twenty (20) paces to the front of the battery-wagon. At the same command, which will be repeated by the detachment commanders, the detachments will move off and form in close column in the same relative order as before, behind the director and markers, (Fig. 28.)

The section being formed for the march, the park will be broken, and it will be moved forward by the command

1. "Forward,"

when the director and markers will move forward, followed in order by the column of detachments, the battery-wagon, the wire-wagon, and the lance-truck.

On the march the section is formed as shown in Fig. 29.

The direction and swiftness of the march will be regulated by the movements of the director and markers, under the orders of the captain.

The section being on the march, to halt it previous to opening station, the chief of section commands

1. "Section."

2. "Halt."

To open station the chief of section will command—

1. "Open station, right, (or left.")

2. "March."

At the second command the battery-wagon will move out of the column to the point indicated, and be followed by the battery-man and three (3) operators; at the same time the wire-wagon and lance-truck will close up to the column of his detachment; the driver of the battery-wagon will unhitch his horses and stand at their heads, and the battery-man will make the necessary ground-connection. To open station, the train being in march, the command will be the same, (1. "Open station, right, (or left.") (2. "March.") At the command "march," the detachments halt under command of the chiefs of detachments; the battery-wagon wheels out of the column in the direction indicated, and the wire-wagon and and lance-truck close up upon the column of detachments and halt. The command will then be

1. " Equip."

2. "March, (or double time, march.")

At the first command, the chiefs of detachments will cause them to face about. At the second command, which will be repeated by the chiefs of detachments, the latter will separate, and move in equal divisions on either side of the train, the operators and two wire-men taking position at and to the rear of the wire-wagon, and the lance-men, bar-men, and pinmen on either side of the lance-truck, where they will take equipments, and face toward the front of the train; the lance-men opposite the rear wheels, the bar-men between the wheels, and the pin-men and the two lance-men who are to deliver lances, opposite the front wheels of the lance-truck. (Fig. 30.) The command will then be given

1. "To your posts."

66

2. March, (or double time, march.")

At the first command the director and markers move forward 20 paces, and the bar-men raise the bar to the right shoulder, the two designated lance-men mount the lance-truck.

At the command "march," the surveyor and pin-men move to the front, and immediately behind the director and markers. The bar-men follow the surveyor and pin-men. At the same time the lance-truck will pass the wire-wagon, and close up upon the bar-men. The lance-men are marched to the rear of the wire-wagon.

At the command

1. Prepare to reel out,"

the director having been instructed by the lieutenant as to the direction and route of the line, moves forward rapidly with the markers, stationing the first marker at a point about 300 feet from the wire-wagon. One of the wire-men takes the end of the wire from the wirewagon, and makes it fast to the wheel of the battery-wagon. (Fig. 31.) The first pinman, under direction of the surveyor, marks the first hole about 30 paces from the batterywagon, a bar-man falls out to make it, and the first lance is delivered by it. The command is then given

1. Reel out."

2. March."

At this command the director moves forward, taking the second marker, and stationing him at a second point on the route, visible to the first marker. The distances between the markers thus placed will be necessarily regulated by the topography of the country. The lieutenant moves forward; the surveyor follows on the line indicated by the markers, and is accompanied by two pin-men.

The first pin-man, with forty marking-pins (for one mile of line) follows the surveyor, who paces the distance of 55 steps, or 132 feet, the distance between poles, and indicates the points where the pin-man shall place the pins.