current is generated in the coil wire. Now if, to the bind ing screws, wires be attached, communicating in like man ner with an apparatus precisely similar to that described, it w.i.ll Ite Ilear that there will be a closed circuit of wire, and our induced current will pass through the second tele phone and back again to the first one. But in passing through the coil in telephone No. 2, it modifies the mag netization of the magnet and increases or diminishes its attraction. for the diaphragm.
... r the diaphragm. Hence every vibration made by the first disk is repeated by the' second one, and what ever sound produces the vibration of one is transmitted to and reproduced by the other. Our large engraving, Fig. 2, affords an excellent idea of ltow the instrument is used, and also of about the extent of circuit over which it is known to be capable of successful operation. We suppose the closed wire circuit to extend from New York to Newark, thence to Paterson and Yonk ers, and back to New York, a distance of about 50 miles air line, or some 70 miles by railway. The figure marked New York may be considered as a public speaker delivering a lecture to be heard in the towns mentioned. He talks into one telephone while he holds another to his ear, in order, for example, to hear the applause, etc., of his auditory; or he may be maintaining a discussion or debate, and he then hears his adversary's replies or interruptions. Now, at N ew ark there is simply a reporter, who takes down the speech phonographically; the words pass on through that telephone and reach Paterson. Here we show two persons, each with a telephone, the two instruments being connected. Each hears from his own instrument. Perhaps, in the future, operatic or concert companies and lecturers, instead of trav eling over the country, will simply send out telephones enough to present each person of their audience in a distant city with an instrument apiece, and do their talking and singing once for all in the metropolis. In Yonkers we show three persons listening to a single instrument, which may be done in a very quiet room. Finally, in a side sketch we show how the telephone is arranged to serve as a speaking trumpet between office and shop in a factory. Of course for a long circuit there would be earth connections instead of the wire loop. The telephone has advanced considerably beyond the sta tus of a "b eautiful scientific toy," which many hastily pro