The means employed by Mr. Varley to produce these interruptions are the same which are in use in several electrical instruments, and especially in chronographs--an electro-magnetic tuning-fork, regulated so as to emit the sound required. This tuning-fork may, by acting as contact-breaker, react on the primary current of the induction coil; if the number of the tuning-forks equals that of the musical notes which are to be transmitted, and if the electro-magnets which set them in motion are connected with the key-board of a piano, it would be possible to transmit a melody to a distance by this system, as well as by that of Mr. Elisha Gray. The peculiarity of this system consists in the reproduction of sounds by the action of a condenser, and we shall presently see that this idea, adopted by Messrs. Pollard and Gamier, led to interesting results. _Singing Condenser of MM. Pollard and Garnier._--This instrument, which astonishes all who hear it, attracted public attention in London some time ago. It is difficult to say why its fame was not greater, since much attention has been bestowed on less curious instruments. It is a fact that we have been able, thanks to MM. Pollard and Garnier, to hear songs issue from a sort of copy-book, so as to become audible throughout the room. The songs thus reproduced are certainly not always perfectly true; yet when the person who sings into the sender is a musician, and understands how to make use of it, the condenser in question will emit sounds somewhat resembling those of the violoncello or the hautbois. The singing instrument consists of a condenser K, formed of thirty sheets of paper, laid one over the other, from nine to thirteen centimètres in thickness: between these, twenty-eight sheets of tinfoil, from six to twelve centimètres thick, are intercalated, so joined as to form the two plates of the condenser. For this purpose the pair sheets are joined together at one end of the copy-book, and the odd sheets at the other end. This system is fastened to a stiff _carton_, after taking care to bind it with a strip of paper, and the sheets of tinfoil are joined to the two ends of the condenser by two copper rims D, D, which are provided with terminals for the circuit wire, and in this way the singing instrument is constructed. A somewhat heavy weight, placed upon the condenser to compress the sheets, does not in any way prevent it from working; and this vitiates the theory first put forward to explain its effects, that the sheets were moved by attraction. [Illustration: FIG. 5.]