of course, only approximate. For the subsistence of these and all other working parties proper arrangements must be made, but that is a matter which need not be entered upon here, as the same care would have to be taken of working parties at any other duty, and is simply commissary and quartermasters' work.

A party or parties to cut and prepare the poles should follow closely upon the diggers and should be strong enough to supply poles for the line as fast as the holes are dug. No rule can be given, the number of men and amount of transportation depending entirely upon the work to be done, the distance posts have to be transported, &c. Axes are the only tools needed. Wagons can be fitted for transporting poles by removing the bed or box and substituting a long reach for the ordinary one. If the ground be impracticable for wagons, posts may be hauled two or three at a time upon a contrivance shown at Fig. 20, which can be made on the ground by any handy Fig. 20.

man. When the holes have been dug and the posts delivered for, say, ten miles, the insulators should follow and be attached, one man (or two, if more than one wire is to be put up) doing the work of attaching them, and the party which is to erect the posts should follow closely the insulators, erecting the poles as soon as the insulation is attached, in order that they may be out of the way of such accidents as would injure or destroy them if left upon the ground.

The number of men necessary in these parties will depend upon the size and weight of the poles, but cannot be less than five men and a foreman, and only so few when the poles are of very light wood, white-cedar, for instance, and well seasoned. For green posts, of oak, locust, or chestnut, ten men will be needed. In working the foreman or à mau places the foot-plate in the hole on the side opposite to that on which the post lies; the men, seizing the post with their hands, raise its top from the ground breasthigh and thrust its foot against the foot-plate: the man whose duty it is places the shears so as to support the post in that position, when the men quit their hold, and, taking their pikes, arrange themselves on opposits sides of the post, and, using their pikes, at once raise the post, which slips into the hole. This releases the foot-plate, which is removed; the cant-hook

is applied and the post turned, if necessary, to the proper position, i. e., with the insulator on the side next the road, or the cross-arm (if any) at right angles thereto. Two men with shovels and tamping-bars fill the hole with earth and ram it solid; then the post is ready for the wire. In this, as, in fact, in all parts of the work, no pains should be spared to make the work thorough. The foreman must see that the posts are perpendicular; that the insulation is properly attached and in proper position when the posts are erected; that the holes are filled and the earth well rammed, and the surface of earth in contact with the post higher than that surrounding it, so as to turn the water away from it.

The wire-party should consist of foreman and six men, with a wagon (or, on railway, a truck) to carry the wire and wire-reel. The wire being in the wagon and the reel in place, the wire-man places a coil upon the reel, cuts the tie-wires, passes the end (taking care that it be the outside end) of the wire to the follower, who attaches it to the first post or such other starting-point as may be designated, the driver starts his team, and the wire is drawn from the reel, the wire-man applying so much friction to the wire or reel (by a clutch or brake) as may serve to give the wire proper tension; the follower, at from thirty to forty yards in the rear, carries the wire to the foot of the pole, and the climbers, four in number, carry the wire to the top of the post and attach it to the insulator, each man taking the fourth post from the one with which he starts. If more than one wire is to be put up, such a party will be needed for each wire, and the first party will put its wire on the insulator farthest from the route, that is, on the end of the cross-arm away from the road, or the insulator on or nearest the top of the post, so that the work of the first party shall not be in the way of the second. The foreman must see that the wire is delivered with only so much slack as is necessary, and does not hang too low when put up; that the joints or connections are properly made, and generally that the work is well and promptly performed. In putting up two wires on one line, the two parties can be kept within one-fourth of a mile of each other, and under the charge of the same foreman or officer.

Connections, joints, or splices, variously so called, may be made in any manner which will give a contact equal in area to a cross-section of the conducting-wire, so that the conduc

Fig. 21.

tivity of the line shall not be less at that point than where the wire is continuous. The connection in common use is shown at Fig. 21, and is made by bending the ends of the two lengths to be connected at right angles, and then wrapping each end snugly around the other wire in a close spiral. Another form that has been a favorite with some constructors is made by winding the ends of the two lengths

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around each other in long spirals which interlock. A third, used in England and the provinces, and called the " Britannia joint," is shown at Fig. 22, and no description is

Fig. 22.

necessary.

The joint first shown is, all things considered, the best for military telegraphs. The wire of a joint should always be cleaned, and, when practicable, the joint soldered.

CHAPTER V.

The line being erected, the maintenance thereof must be at once cared for, and the force necessary for this purpose must be determined by the circumstances of the case. No rule can, therefore, be given. Repairmen or patrols must be located at an office in order that their operations may be directed by the officer or person in charge from any point where he may be must be mounted, or provided with other means of rapid transportation, and be equipped with hatchet, insulators, pulleys, and rope, or other device for bringing together the ends of a broken wire, climbers, file, pliers, and a small quantity of line-wire. Immediately upon the discovery of a fault, the repairman on either side of its supposed location should proceed at once in its direction, and go until he finds and repairs it or meets the man from the opposite side of the fault. In addition to this duty, the repairmen should have charge of a certain length of line, and should go over it often, replacing broken insulators, if any, trimming away branches of trees, shrubs, or climbing-vines, (in short, preserving the wire from any contact except with insulators,) and generally maintaining the line in good condition. On long lines this work should be under the care of a chief, who should be an operator capable of working and testing a line, who should be held responsible for the proper condition of the line at all times and be required to make proper reports of all work done under his direction.

The working of a line should be the duty of a superintendent, with as many assistants as there may be circuits in the line, if more than one, and as many operators as the business to be transmitted renders necessary. At offices that are to be kept open during the day only, and where a small amount of business is to be transacted, a single operator only is needed; but where the labor is continuous, eight hours a day is as much as a man can do and do well, and this should be broken into two watches or tours. Such lines will necessarily be worked by some of the usual modes, and are treated of as worked on the Morse plan, as the most flexible, requiring the least machinery and equipment, and the skilled labor for which is the most easily procurable.

The superintendent is of course responsible for the working and maintenance of the whole, each assistant to him for so much thereof as shall be his charge, and the manager of each office to his immediate superior for his office and subordinates. A system of reports should show monthly the state of the line, condition, property received, expended, and on hand, labor employed, rate paid, work done, and, if money received, its amount, from what sources, how disposed of, and such other information as may be necessary or desirable.

Where military operations are carried on along a line of railway, telegraphs will always be needed to facilitate the operation of the railway as well as to maintain communication between the force and its base, and to render the service effectual a single officer should have control of the movement of trains and charge of the railway wires, if practicable.

On military lines, the communications of the commander, or those addressed to him on military business, must have precedence over all others, those of subordinate officers next, and private or ordinary communications, if transmitted at all. must go only when the line is not otherwise occupied, and should be subjected to rigid scrutiny to prevent the transmission of intelligence of an improper character. When a railway is used, and no wire is set apart for its exclusive use, the messages of the master of trains or transportation concerning the

business of his office, affecting, as they do, the movement or supply of the Army, are o great importance, and take precedence of all except those of the commander of the forces.

The alphabet or code to be used on these lines may be that hereafter described; but, as the amount of business to be transacted will always be large, it may be necessary to employ skilled Morse telegraphers and use that code. For information concerning it and the best method of acquiring skill in its use, the student is referred to the work so often referred to already, the Modern Practice of the Electric Telegraph, by F. L. Pope; to Wood's Plan of Telegraphic Instruction, and Smith's Manual of Telegraphy.

PART II.-FIELD-LINES.

CHAPTER VI.

The materials for a line of field-telegraphs (by which is meant a line to be used in the presence of an enemy and for the purpose of placing the commanding officer of a force in constant communication with all parts of his line) differ from those for permanent lines chiefly in point of size and capability of being quickly erected and put into use and as quickly removed when the occasion for the line no longer exists. These materials must be, therefore, such as can be transported with the troops, handled by enlisted men, and when in line worked by enlisted men or officers.

The supports for a field-line may be either natural-such as trees-or artificial poles or lances. The use of the former should be guided by the same rules as for permanent lines, the circumstances being the same. The artificial supports must be of such size and weight as may be transported, and at the same time have length sufficient to carry the wire above the reach of mounted men or wagons and strength enough to endure such handling as under the circumstances they would be likely to receive, as well as to bear the weight and strain of the line-wire. To meet these requirements they must be made of a material at once light and elastic, and the timber best adapted seems to be spruce or cypress, either of which, when well seasoned, fulfills very nearly these conditions. The size may vary within cer tain limits, but that adopted in the field-telegraph trains of the United States Army is 17 feet long, 24 inches diameter at the butt, and 1 inches diameter at top, the butt tapering to a blunt point and the top secured by a sheet-iron ferrule 3 inches in length. Such a lance, of cypress, weighs about eleven pounds, and of spruce a trifle less, and two hundred and fifty of them, together with insulation for ten miles of wire and tools for the erection of a line of that length, can be carried on a truck made for the purpose and readily handled by six mules or four horses. A field-line should be supported by forty such lances to each mile of wire, but in emergency, or upon favorable ground, this number may be reduced to thirtyfive or even to thirty without serious difficulty resulting.

In the matter of insulators for field lines there is small room for choice. Glass and por celain, the substances in common use for permanent lines, are unfit because of their fragility; the common resins, paraffine, &c., are unfit because of the difficulty of applying them, and there remain only the gums, caoutchouc, gutta-percha, and ballata. Of these gutta-percha becomes friable when long exposed to the sun, rain, and wind, and in such condition loses its good qualities; its use, therefore, is precluded. Ballata is not well proved, and no preparation thereof is yet offered which has consistence enough for the purpose. Caoutchouc when raw becomes viscid and loses form under summer temperatures, but in the prepared form known as vulcanite, ebonite, or, more familiarly, "bone-rubber," resists any heat less than that of boiling water, and has strength and consistence enough for the purpose, at the same time retaining to a great degree the non-conducting power of the raw or unmanufactured gum, making it the most desirable material for insulators for this service.

The form of the insulator is a matter of choice, two conditions only being of importancethat the outer surface shall shed rain and that there shall be an inner surface which shall remain dry, in order that there shall be between the wire of the line and the lance (which, when wetted by rain, becomes a partial conductor) a nou-conducting surface This can be obtained only by protecting a part of the surface of the ebonite from moisture, which, if allowed to reach it, forms a film over its surface and acts as a conductor. The formation of this film may be at least partially prevented by occasionally dipping the ebonite insulator into melted paraffine, the coating of that substance which the ebonite receives acting to prevent the formation of a continuous film of moisture, breaking the water into drops, at the same time that it preserves the surface of the ebonite from "weathering," and so acquiring a spongy character favorable to the formation of the water-film.

Various forms or patterns have been used, one of which was a simple cap of flexible vulcanite to fit over the top of the lance, both lance and cap having a cleft in which the wire rested and was secured by being wound around the outside of the cap; another, which consisted of a wire suspender or clamp" of ebonite armed with a gimlet-pointed screw, by

which it was affixed to the lance or other support; another consists of a spike, which passes through the top of the lance or is driven into a tree, and a suspender formed in part of ebonite. Each has merit, but neither gives entire satisfaction. It would seem evident that the fewer parts the insulator consists of, the better, as less liable to become useless by fracture; that the insulator should be readily attached to and detached from the lances or other supports, and that the device for grasping the wire should be such that the wire could be easily placed therein and not readily displaced, and be held without bending.

Substitutes for any regular form of insulator can be made from many materials, and the ingenuity of the officer must be his reliance. The non-conducting properties of bodies being known, he must make use of the best within his reach, and turn it to such advantage as he may. An insulator of fat pine," or any wood saturated with resin, may be made to answer a good purpose while the saturation continues. Loops of cotton, linen, or silk fabric suspending the line-wire will insulate it sufficiently during dry weather, and if saturated with oil will prove efficient on a short line even in rain or fog. Saturation with paraffine would be more effective than with oil, and a quantity of this substance might be comprised in the list of supplies for a field-train with much propriety. Wire for field-telegraphs must be light, flexible, and strong enough to bear a tension which will reduce the deflection or "sag" between lances 70 yards apart to 2 feet. Iron is the only material which answers the purpose at moderate cost, and an iron wire, drawn from charcoal rods to No. 15, American gauge, has been adopted for use by the United States. A mile of this wire, joined up and the joints soldered, makes a coil 18 inches in diameter inside, 4 inches in height, and 3 in thickness, and weighing but 75 pounds. The American compound telegraph-wire, a patented article, consists of a steel core, with a coating of copper, and when drawn to No. 18 size has, when new, equal strength and greater conducting capacity than No. 15 iron wire, but is not well adapted for field-use, being less flexible than the iron, breaking more easily if bent, and deteriorating rapidly in consequence of the oxidation of the steel core, wherever moisture reaches it, which it can scarcely fail to do, as the copper coating or envelope opens to the steel whenever the wire is rudely bent or handled.

For use where, for any reason, it is impracticable or inexpedient to erect a line upon supports, and therefore necessary to lay it along the ground, conducting wire must be provided which is insulated throughout its entire length. Such a wire has been referred to heretofore as office-wire," but especial pains needs to be taken to provide for field use, and the various descriptions of such insulated conductors, their characteristics, method of manufacture, strength, flexibility, and conducting capacity understood. Copper, from its high conductivity, is the metal used, and is strengthened in various ways. One device is to form a conducting strand of five wires, the center one of steel, for strength, and the outer ones laid spirally around the center, of copper. Such a strand, made of No. 30 wire, will have the strength of a No. 14 iron wire and the conducting capacity of No. 8, or very nearly, and may be insulated in any manner, like a single wire. Kerite, a preparation of caoutchouc, not yet well known or proved by use, has shown valuable qualities under experimental tests, resisting the action of the atmosphere, which usually destroys such preparations, and is highly recommended by many competent telegraphers and electricians. A single copper wire, covered with a layer of hemp fibers laid parallel to it, and the whole with a spiral cov ering of cotton, (cotton and hemp being saturated with paraffine,) is light, quite strong, (sufficiently so to sustain itself in spans 200 to 300 feet long,) and sufficiently well insulated for ordinary use. The insulation can be kept up by occasionally passing the wire through a bath of melted paraffine. Another device for retaining the hemp fibers in place has been used by some manufacturers, viz, braiding flax around it, and a preparation of paraffine and coal-tar, known as "Bishop's compound,' is used instead of the pure paraffine. For use under water, gutta-percha is the best insulating material known, improving when submerged, instead of deteriorating. For subterranean use the same can be said.

CHAPTER VII.

Instruments for field-lines must be simple, easily placed in position for use or removal, easily adjusted, and strong. Several varieties have been tested by the Signal-Office, but the one from which the best results have been obtained is a form manufactured by Messrs. L. G. Tillotson & Company, in New York, and known as the "box-sounder," shown in Fig. 23. Another form, known as the Caton instrument, shown in Fig. 24, consists merely of an electro-magnet mounted horizontally and provided with an armature, the vibrations of which, when attracted to the poles of the magnet or withdrawn therefrom by the tensionspring, give the sounds by which the signals are recognized; a key by which the circuit is opened and closed in signaling; a device by which the circuit is kept closed, except when the key is in use, and screw-posts by which to attach the line-wires, the whole contained in a case to protect it during transportation. The one shown in the cut is of convenient size, being about 6 inches long and 24 in width and length.

Batteries for field-use need not be so powerful as for permanent lines, and others which require the use of such powerful excitants as sulphuric and nitric acids, and must not be composed of glass or other fragile material. These conditions render the Grove and Bunsen batteries unsuitable and leave the Daniells only for use in some one of its various modifications. The form used at present by the United States Signal Service is an adaptation of the Daniells, and consists of a wooden trough divided into cells by wooden partitions, the whole Fig. 23.

being rendered non-conducting and impervious to water by saturation with paraffine; a thin copper plate, near the bottom of each cell, having underneath it a layer one-fourth of an inch thick and above it a layer three-fourths of an inch thick of crystals of sulphate of copper; a sponge, saturated with water and filling the cell to within an inch of the top, upon the upper surface of which is sprinkled white vitriol, (sulphate of zinc,) and a zine plate, which rests upon the sponge. The cells are 5 inches square, being the same in length, breadth, and depth; the top, bottom, and sides of the box or trough containing them, 1 inch

and the partitions between the cells one-fourth of an inch in thickness. The copper plates are 4 inches square and about one-sixteenth of an inch in thickness, and to each one is attached a copper wire, insulated with gutta-percha or caoutchouc, of sufficient length to reach the zine of the adjoining cell. The zinc plates are 4 inches square and 1 inch in thickness, and are furnished with thumb-screws for connecting with the wire from the copper element of the next cell. The cover of the box or trough is hinged, and when closed is secured by hasps and staples. When closed and secured it presses firmly upon the zine plates and prevents any displacement of the parts of the battery. It will be seen that this is substantially the Daniells copper-zinc pair, the sponge taking the place of the porous earthen cup and the trough or box that of the glass or earthenware containing-vessel. The superposition or the zinc prevents the copper solution from reaching it, and the battery so arranged works with little diminution of force as long as any of the crystals of blue vitriol remain undissolved. It is only necessary to add a little pure water from time to time, to supply the waste by evaporation or leakage. When the cell is filled 1 inch in depth with the crystals, it will work from forty to sixty days without renewal. When necessary to renew the battery, the materials must be removed, the sponges well cleaned, and the whole