The General Feolures of the Sys/ern are as follows: A tele graph-line extends along the side of the railroad-track at about the distance of S or To feet from the track. The poles, which are much smaller than ordinary telegraph-poles, are from To to 16 feet high. At the top of each pole is placed an insulator on which is strung, a single galvanized-steel (or iron) telegraph-wire. The equipment of the car is extremely simple, mainly consisting in the use of an iron or brass rod or tube, about half an inch in diameter, extending- along on each side of the car, under the eaves (or, instead of employing rods or tubes, in many cases the metal roof of the car is used), and connected by an insulated copper wire with the battery' and instruments in the car, which are grounded through the wheels and track by a single wire run through the floor, as shown in Figure 2 (pi. 59), which A is the roof contact, B the rod or strip of metal, C the secon dary or induction coil, D the double-pointed key with extra contact, E the telephone receiver, F the primary circuit, G the ground contact on axle box, and the battery.
The Instruments, which are small and compact, consist of a telephone receiver (attached to the head of the operator), a small secondary coil and " buzzer," and an ordinary telegraphic key. The last two arc placed on a board about ro or 13 inches square, which is carried on the arm of the operator (/5/. 39, jig. 3). The battery is contained in a small box which may be put in any convenient place. Figure r, which shows the train telegraph-operator sending a message on a moving train, gives an excellent idea of the system in actual practice. The sending apparatus is held in the operator's hands, while the receiver is attached to his ear.
Advantages of the the adoption of this system all trains on the line of railroad employing it, whether they be in motion or at rest, or whether they be on the main track or on sidings, arc susceptible of be ing placed in instantaneous communication with the division terminal sta tion, and orders may be despatched to any or all of them, regardless of their position. Furthermore, not only the train-despatcher is enabled to com municate his orders to the trains within his division, but also the train officials are enabled similarly to communicate with the train-despatcher; and they may thus reciprocally inform one another of any accident or other unusual occurrence upon the line.
The system has the incidental advantage of so admirably controlling the movements of trains that it affords a reliable• safeguard against collis ions. Under the ordinary system, if the station-operator neglects to give an order when the train is at the station, the opportnnity is g-one, and a serious accident may be the result. With telegraphic communication be
tween fixed stations and moving trains, the neglect may be remedied at any moment. Furthermore, 012 single-track roads, which are numerous in the United States, the detention occasioned by holding trains to receive tcleg-rams from delayed trains moving in opposite directions may, by the use of train telegraphy, be entirely avoided without incurring the slightest risk, and thereby the capacity of these roads may be largely increased. .Moreover, by this system travellers may send and receive telegraphic com munications while in transit, which, though of minor value compared with greater safety of train operation, is of importance as an element contribut ing substantially to the perfection of modern railway-trayelling. Until the advent of this system the traveller on a moving train was isolated; 110W he is in constant communication with the outside world.
Briefly summarized, the advantages claimed for this most ingenious and novel extension of the art of telegraphy are as follows: It will render it possible to move trains safely at shorter intervals and with greater immu nity from accident than any system heretofore devised; its first cost and expense of maintenance will be much less than are required for any other thoroughly efficient system; it will have the immeasurable advantag,e of enabling the train-despatcher to communicate distinct and definite orders to any and all trains, wherever they may be, while the range of any sig nalling system, no matter how perfect, must necessarily be limited to a few prearranged orders at fixed points.
The art of telegraphy has become a necessary factor in the conduct of public and private business, and plays an important part in the conduct of military operations. To meet the requirements of modern warfare, a spe cial branch of telegraphic service, termed " field telegraphy," has been devised, and developed to a high state of efficiency. Furthermore, the use of the telegraph for the transmission of simultaneous meteorological obser vations made at various distant points has proved of the utmost value to agriculture and commerce.
Telephones: Reis's 1876 there has come into use in all civilized countries an important modification of the electric telegraph by which articulate sounds are transmitted over considerable dis tances. The apparatus employed is known as the telephone. The first approach to a practical acoustic teleg-raph was made by Philipp Reis, a German, as early as 186o, who devised the apparatus shown in several modifications on Plate 59 (figs. 4, 5), by which musical sounds were trans mitted and reproduced at a distance; but it is still a question whether his apparatus ever transmitted and reproduced articulate sounds.