In this new form, the moveable carbon which is required to produce the variable contacts is at C, at the end of a horizontal bar B A, properly balanced so as to move up and down on its central point. The support on which the bar oscillates is fastened to the end of a spring plate in order that it may vibrate more easily, and the lower carbon is placed at D below the first. It consists of two pieces laid upon each other, so as to increase the sensitiveness of the instrument, and we represent the upper piece at E, which is raised so as to show that when it is desired only one of these carbons need be used. For this purpose the carbon E is fastened to a morsel of paper, which is fixed to the little board and contributes to the articulation. A spring R, of which the tension can be regulated by the screw _t_, serves to regulate the pressure of the two carbons. Mr. Hughes recommends the use of metallised charcoal prepared from deal.[14] The whole is then enclosed in a semi-cylindrical case H I G, made of very thin pieces of deal, and the system is fixed, together with another similar system, in a flat box, M J L I, which, on the side M I, presents an opening before which the speaker stands, taking care to keep his lower lip at a distance of two centimètres from the bottom of the box. If the two telephones are connected for strength, and if the battery employed consists of two cells of bichromate of potash, it is possible to act so strongly on the current, that, after traversing an induction coil only six centimètres long, a telephone of Bell’s square model can be made to speak, so as to be heard from all parts of a room; a speaking tube, about a yard long, must indeed be applied to it. Mr. Hughes asserts that the sounds produced by it are nearly as loud as those of the phonograph, and this is confirmed by Mr. Thomson. M. Boudet de Paris has lately invented a microphone speaker of the same kind, with which it is possible to make a small telephone utter a loud sound. An induction coil, influenced by a single Leclanché cell, must be employed.