some systems of multiple telegraphy. Such adjustments are known to telegraphic experts.
By means of a tube with multiple gaps it is 365possible to work the trembler and also the signaling or other apparatus direct on the circuit which contains the tube, but I prefer when possible to work with the single-gap tube and the relay, as shown. With a sensitive370 and well-constructed trembler it is also possible to work the trembler with the single-gap tube in series with it without the relay.
In derivation on the terminals of the relay n is placed an ordinary platinoid resistance 375double-wound (or wound on the "bight," as it is sometimes termed) coil q of about four times the resistance of the relay, which prevents the self-induction of the winding of the relay from affecting the sensitive tube.
380The circuit actuated by the relay contains an ordinary battery r of about twelve cells and the trembler p, the resistance of the winding of which should be about one thousand ohms, and the nucleus ought preferably 385to be of soft iron, hollow and split lengthwise, like most electromagnets used in telegraph instruments. In series or derivation from this circuit is inserted the telegraphic or other apparatus h which one may desire to work. 390It is desirable that this instrument or apparatus, if on a derivation, should have a resistance equal to the resistance of the trembler p. A platinoid resistance h1 of about five times the resistance of the instrument is 395inserted in derivation across the terminals of the instrument and connected as close to the same as possible. In derivation across the terminals of the trembler p is placed another platinoid resistance p1, also of about five times 400the resistance of the trembler. A similar resistance p2 is inserted in a circuit connecting the vibrating contacts of the trembler. In derivation across the terminals of the relay-circuit it is well to have a liquid resistance s, 405which is constituted of a series of tubes, one of which is shown full size in Fig. 8, filled with water acidulated with sulfuric acid. The number of these tubes in series across the said terminals ought to be about ten for a 410circuit of fifteen volts, so as to prevent, in consequence of their counter electromotive force, the current of the local battery from passing through them, but allowing the high-tension jerk of current generated at the opening of 415the circuit in the relay to pass smoothly across them without producing perturbing sparks at the movable contact of the relay. It is also necessary to insert a platinoid resistance in derivation on any apparatus one may be 420working on the local circuits. These resistances ought also to be inserted in derivation on the terminals of any resistance which may be apt to give self-induction.
I have hitherto only mentioned the use of 425cylindrical reflectors, but it is also possible to use ordinary concave reflectors, preferably parabolic, such as are used for projectors.
It is not essential to have a reflector at the transmitters and receivers, but in their absence the distance at which one can communicate430 is much smaller.
I find it convenient when transmitting across long distances to make use of the transmitter shown in Fig. 9.
t t are two poles connected by a rope t1, to435 which are suspended by means of insulating suspenders two metallic plates,t2 t2 preferably in the form of cylinders closed at the top, connected to the spheres e (in oil or other dielectric, as before) and to the other balls t3 in 440proximity to the spheres c1, in communication with the coil or transformer c. The balls t3 are not absolutely necessary, as the plates t2 may be made to communicate with the coil or transformer by means of thin insulated wires. The445 receiver I adopt with this transmitter is similar to it, except that the spheres e are replaced by the sensitive tube j and plates k, while the spheres t3 are replaced by the choking-coils k1, in communication with the local450 circuit. It may be observed that, other conditions being equal, the larger the plates at the transmitter and receiver and the higher they are from earth and to a certain extent the farther apart they are the greater is the455 distance at which correspondence is possible.
When transmitting through the earth or water, I use a transmitter as shown in Fig. 10. I connect one of the spheres d to earth E, preferably by a thick wire, and the other460 to a plate or conductor u, suspended on a pole v and insulated from earth; or the spheres d may be omitted and one of the spheres e be connected to earth and the other to the plate or conductor. At the receiving-station, 465Fig. 11, I connect one terminal of the sensitive tube j to earth E, also by a thick wire, and the other to a plate or conductor w, preferably similar to u. The plate w may be suspended on a pole x and must be insulated from earth. The470 larger the plates of the receiver and transmitter and the higher from the earth the plates are suspended the greater is the distance at which it is possible to communicate. When using the last-described apparatus, it is not475 necessary to have the two instruments in view of each other, as it is of no consequence if they are separated by mountains or other obstacles. At the receiver it is possible to pick up the oscillations from the earth or water480 without having the plate w. This may be done by connecting the terminals of the sensitive tube j to two earths, preferably at a certain distance from each other and in a line with the direction from which the oscillations485 are coming. These connections must not be entirely conductive, but must contain a condenser of suitable capacity—say one square yard of surface. Balloons can also be used instead of plates on poles, provided they carry490 up a plate or are themselves made conductive by being covered with tin-foil. As the height to which they may be sent is great, the distance at which communication is possible be-