The invention of this telephone dates, as we have seen, from 1860, and Professor Heisler speaks of it in his treatise of technical physics, published at Vienna in 1866; he even asserts, in the article which he devotes to the subject, that although the instrument was still in its infancy, it was capable of transmitting vocal melodies, and not merely musical sounds. The system was afterwards perfected by M. Van der Weyde, who, after reading the account published by M. Heisler, sought to make the box of the sender more sonorous, and to strengthen the sounds produced by the receiver. He writes as follows in the ‘American Scientific Journal:’ ‘In 1868, I caused two telephones to be made, similar to those I have described, and I exhibited them at a meeting of the Polytechnic Club of the American Institute. The transmitted sounds were produced at the farthest extremity of the Cooper Institute, quite outside the hall in which the audience sat: the receiver was placed on a table in the hall itself. The vocal airs were faithfully reproduced, but the sound was rather weak and nasal. I then tried to improve the instrument, and I first obtained stronger vibrations in the box K by causing reverberation from the sides of the box, by means of hollow partitions. I next intensified the sounds produced by the receiver, by introducing several iron wires into the coil, instead of one. These improvements were submitted to the meeting of the American Association for the Advancement of Science, which was held in 1869, and it was considered that the invention contained the germ of a new method of telegraphic transmission which might lead to important results.’ This opinion was soon afterwards justified by the discoveries of Bell and Elisha Gray. _Messrs. Cecil and Leonard Wray’s Telephone._--This system, represented in figs. 2 and 3, is simply an improvement on that of M. Reiss, with the object of intensifying the effects produced. The sender is provided with two membranes, instead of one; and its receiver, instead of being formed of a single iron wire covered with a magnetising coil, is composed of two distinct coils H, H′ (fig. 2), placed in the same straight line, and within which are two iron rods. These rods are fastened by one of their ends to two copper disks A, B; these disks are maintained in a fixed position by screws I, I′, and the two other extremities of the rods, between the coils, are opposite each other, not touching, but divided by a very small interval. The instrument is set upon a sounding-box, in which there is a hole T in the space corresponding to the interval between the coils: these coils communicate with four terminals, which are connected with the electric current in such a way that the adjacent poles of the two rods are of opposite polarity, thus forming a single magnet, divided in the centre. It seems that by this arrangement the sound produced becomes much more distinct. [Illustration: FIG. 2.] [Illustration: FIG. 3.]