The receiving telephone somewhat resembles that of Mr. Bell, yet it presents some differences which can be understood from the examination of fig. 29. The magnet N S is horseshoe in form, and the magnetising coil E only covers one of the poles, N: this pole is precisely in the centre of the vibrating plate L L, while the second pole is near the edge of this plate. The size of the plate itself is considerably reduced: its superficies is about the same as that of a five-franc piece, and it is enclosed in a kind of circular groove, which keeps it in a definite position. In consequence of this arrangement the handle of the instrument is of solid wood, and the vacant space for the electro-magnetic system is somewhat larger than in the Bell model; but an arrangement is made for subduing the echo, and there is a kind of sounding-box to magnify the sound. It is evident that the relation which the electro-magnetic system bears to the vibrating disk must increase the sensitiveness of the instrument; for as the pole S is in close contact with the disk L L, the latter is polarised, and becomes more susceptible to the magnetic influence of the second pole N, which is separated from it by an interval not exceeding the thickness of a sheet of coarse paper. In Mr. Edison’s two instruments, the receiver and sender, the upper part C C, corresponding to the vibrating disk, instead of being fixed by screws to the handle, is screwed on to the handle itself, which makes it much more easy to dismount the instrument. Mr. Edison has varied the form of his instruments in many ways, and their cases have of late been made of metal with a funnel-shaped mouthpiece of ebonite. When Mr. Edison had ascertained, as indeed Mr. Elisha Gray had done before him, that induced currents are more favourable to telephonic transmissions than voltaic currents, he transformed the currents from the battery which passed through his sender into induced currents by making them pass through the primary circuit of a carefully insulated induction coil; the line wire was then put into communication with the secondary wire of the coil. We shall afterwards describe some experiments which show the advantages of this combination: for the present we can only point out the fact, for it is now an integral quality of almost all the systems of battery telephones. _Edison’s Chemical Telephone._--The curious and really useful effects produced by Mr. Edison with his _electro-motograph_ prompted, about the beginning of the year 1877, his idea of applying the principle of this instrument to the telephone for the reproduction of transmitted sounds; and he obtained such interesting results that the author of an article on telephones, published in the ‘Telegraphic Journal,’ August 15, 1877, put forward this invention as one of the finest of the nineteenth century. It certainly appears to have given birth to the phonograph, which has lately become famous, and has so much astonished men of science.