‘Since on this system the voice is not required to _produce_, but only to _direct_ the electric current generated by a battery, the intensity of the sound received might in theory be increased at pleasure. I have in fact been able to make the receiver emit very powerful sounds, and I think that this advantage greatly counterbalances the necessity of employing a battery, and a somewhat delicate sending instrument. Unfortunately it can only be used for moderate distances. Assuming that any displacement of the transmitting membrane increases the resistance to a degree equivalent to five or six hundred yards of wire: if the line is five hundred yards long, the intensity of the current will be reduced by one half, and the receiving membrane will take up a fresh position, considerably differing from the first; but if the line is three hundred miles in length, the intensity of the current will only be modified by a thousandth part. An immense battery must therefore be employed in order that this variation may be translated by a sensible change in the position of the receiving membrane.’ (See ‘Comptes Rendus de l’Académie des Sciences,’ February 18, 1878.) M. J. Luvini, in an article inserted in ‘Les Mondes,’ March 7, 1878, has suggested a system of rheotome by means of a current, for battery telephones, which, although complicated, possibly offers some advantages, since it produces currents alternately reversed. In this system, the vibrating disk of the sender, which should be in a vertical position, reacts on a moveable horizontal wire, turned back at a right angle, and supporting on each of its branches two platinum points which dip into two bulbs, filled with a liquid of moderate conducting capacity. The two branches of this wire, insulated from each other, are placed in communication with the two poles of the battery, and the four cups into which the platinum wire dips communicate inversely with the line and the earth by means of platinum wires immoveably fixed in the cups. It follows from this arrangement, that when the distances are duly regulated between the fixed and moveable wires, two equal currents will be opposed to each other across the line circuit when the diaphragm is motionless; but as soon as it vibrates, the respective distances of the wires will vary, and it follows from this that there will be a differential current, of which the intensity will correspond with the extent of the displacement of the system, or with the range of vibrations, and the direction will vary with the movements above or below the line of the nodes of vibration. In this way the advantage of the induced currents is obtained.