Mr. Millar, of Glasgow, declares that the effect produced by these telephones depends very much on the nature of the string, the way in which it is attached, and the way in which the membrane is fastened to the mouthpiece. _Improvements made in the String Telephone._--The amazing effects of the Bell telephones have lately brought the string telephones, which were only regarded as children’s toys, again into fashion. Since they have made it possible to transmit to several persons the words reproduced by an electric telephone, means have been sought for combining them usefully with the latter, and the best mode of making them speak on a string presenting several angles has been sought for: it has been shown that, under the usual conditions, these instruments only speak distinctly when the string is stretched in a right line. To solve this problem, it occurred to M. A. Bréguet to make use of a sort of tambourine for the supports, with the string passed through their centre; the sound conveyed by that part of the string which is in connection with the speaking-horn causes the membrane of the tambourine to vibrate, which again communicates the vibration to the next portion of string. In this way the angles may be multiplied at will, and the string may be supported throughout the length compatible with this kind of telephone, which does not exceed 112 yards. M. A. Bréguet has also invented a system of relays to accomplish the same object. He makes the strings terminate in two membranes which close the two openings of a brass cylinder. The sounds reproduced on one of these membranes react upon the other, which vibrates under its influence, as if it were affected by the voice. The cylinder then acts as an ordinary acoustic tube, and its form may be varied at pleasure. M. A. Badet, on February 1, 1878, succeeded in making string telephones in an analogous way, and he used parchment stretched upon frames which acted as resonant boards. The string was fixed in the centre of the membrane, and made with it the angle desired. Several scientific men, among others Messrs. Wheatstone, Cornu, and Mercadier, have long been occupied about these ways of transmission by wire, and Messrs. Millar, Heaviside, and Nixon have lately made some interesting experiments, on which we must say a few words. Mr. Millar ascertained that by means of a telegraphic wire, stretched and connected by two copper wires with two vibrating disks, musical sounds might be conveyed to a distance exceeding 160 yards, and that by stretching these wires through a house, and connecting them with mouth-and-ear holes in different rooms, communication between them became perfectly easy. For the vibrating disks he employed wood, metal, or gutta-percha, in the form of a drum, with wires fixed in the centre. The sound seems to become more intense in proportion to the thickness of the wire.