The effects of the microphone receiver explain the sounds, often very intense, produced by the Jablochkoff candles when they are influenced by electro-magnetic machines. These sounds always vibrate in unison with those emitted by the machine itself, and they result, as I have already shown, from the rapid magnetisations and demagnetisations which are effected by the machine. These effects, observed by M. Marcel Deprez, were particularly marked in M. de Méritens’ first machines. _Other Arrangements of Microphones._--An arrangement such as we have just described has been employed by M. Carette to form an extremely powerful microphone speaker. The only difference is that the stretched membrane is replaced by a thin metallic disk: he fastens one of the carbons to the centre of this disk, and applies to it the other carbon, which is pointed, and held by a _porte-carbon_ with a regulating screw, so that the pressure which takes place between the two carbons may be regulated at pleasure. By this arrangement speech may be heard at a distance from the telephone. In other respects it resembles the telephone sender represented in fig. 5. M. de Méritens has executed the system represented, fig. 45, on a large scale, forming the tube A B of a zinc funnel a yard in length, and in this way he has been able to magnify the sounds, so that a conversation held in a low voice, three or four yards from the instrument, has been produced in a telephone with more sonorous distinctness. The instrument was placed on the floor of the apartment, with the opening of the funnel above, and the telephone was in the cellars of the house.