The form of the sender also is somewhat different from the one we have previously described: the upper part, instead of being horizontal, is rather inclined, as it appears in fig. 3, and the opening E through which the sound has to communicate with the vibrating membrane, occupies a great part of the upper surface of the box, which consequently appears to be somewhat oblique. The second membrane G, which is of caoutchouc, forms a sort of partition which divides the box in two, starting from the upper end of the opening: the inventor states that this will protect the outer membrane D from the breath and other injurious effects, while increasing the force of the vibrations produced on the first membrane, as in a drum. The contact-breaker itself also differs from the one in M. Reiss’s instrument. The platinum disk _b_ is only placed in circuit by means of two slender wires of platinum or steel, which are immersed in two small cups, filled with mercury, and connected with the circuit. In this way, the movements of the membrane D are free, and its vibration is rendered more easy. The circuit is also broken by a little platinum point resting on a lever with a spring-joint, K H, which is above the disk: one end of the lever, which is fixed below a kind of Morse key M I, makes it possible to close the circuit with the hand, so as to give the signal for setting the apparatus to work. _Electric Harmonica._--Long before M. Reiss’s invention, and consequently still longer before that of Mr. Elisha Gray, I mentioned a sort of electric harmonica, and described it as follows in the first edition of my ‘Exposé des applications de l’Electricité,’ published in 1853:-- ‘The power possessed by electricity to set metallic plates in motion and cause their vibration has been used for the production of distinct sounds, which can be combined and harmonised; but in addition to this purely physical application, electro-magnetism has come to the aid of certain instruments, such as pianos, organs, &c., rendering them capable of being played at a distance. So that this extraordinary force may be turned to account in arts which are apparently the least susceptible of any application of electricity. ‘We have already spoken of M. de la Rive’s contact-breaker. It is, as we know, an iron disk, soldered to a steel spring, and maintained in a fixed position opposite to an electro-magnet by another spring in connection with one branch of the current. As the other branch, after passing into the wire of the electro-magnet, terminates in the iron disk itself, the electro-magnet is only active at the moment when the disk touches the terminal spring; at the moment of leaving it, the magnetism ceases, and the iron disk returns to its normal position, and then leaves it again. In this way a vibration is produced, rapid in proportion to the small size of the vibrating disk, and to the greatness of the force produced by the approach of the disk to the electro-magnet.