[Illustration: FIG. 35 (Fig. 3 of Specification 18,644/97).--A self-induction method of sending jerks into a badly insulated line, and arrangement for detecting such jerks by a single-point Coherer.] [Illustration: FIG. 36 (Fig. 4 of Specification 18,644/97).--Another arrangement for sending jerks into a bare or badly insulated line, and connections for Coherer detection.] [Illustration: FIG. 37 (Fig. 10 of Specification 18,644/97).--Another mode of sending a jerk from a spark gap at _j_ into a badly insulated cable or other conductor, which is connected at the other end to a Coherer, the circuit being completed inductively through the air by means of the areas _p_, _p_₁. The dotted lines s represent the switch connection of Fig. 33.] [Illustration: FIG. 38 (Fig. 13 of Specification 18,644/97).--Another method of signalling through a pair of imperfect conductors, such as gas and water pipes _i_, without the above elevated inductive connection.] [Illustration: FIG. 39 (Fig. 3 of Specification 29,069/97).--Diagram of Coherer connection to Syntonic Collector, with capacity shunt for telegraphic instrument.] (4) No. 29,069, 1897. In this patent various methods of connecting up the shunting condenser, whose object it is to transmit all jerks undiluted to the coherer, are shown, all adapted to work with a syntonic resonator (Fig. 39). There is also shown a complete switch (Fig. 40) for effecting the transition from “sending” to “receiving,” exposing the coherer to the full effect of the distant radiator, and completely protecting and isolating it from its home radiator; the switch being so arranged that signalling is impossible unless the home coherer is protected. A rotating commutator is also shown, whose object is to expose the coherer to the full influence of a receiver, especially of a non-syntonic receiver or simple collector, without its being shunted or otherwise interfered with by the telegraphic apparatus; to which, however, immediately afterwards the rotating commutator connects it, and then effects the tapping back. Connections are shown (Fig. 41) for a complete sending and receiving station on this plan with a syntonic radiator and resonator indicated (though not to scale). But with syntonic resonators the revolving commutator method is not found to be necessary; the sending and receiving switch, together with the closed box for protecting the coherer in an instantly accessible manner is therefore the chief feature of this diagram. [Illustration: FIG. 40 (Fig. 6 of Specification 29,069/97).--Switch at a Sending and Receiving Station, to change all the connections with a protected Coherer from receiving to sending by depressing the knob _l_.] [Illustration: FIG. 41 (Fig. 7 of Specification 29,069/97).--Diagram of connections at a protected Coherer Station with Syntonic Radiator and Collector.] EARLIER TELEGRAPHIC ADVANCES.