The topmost row of all sends through the wires a negative current of known strength; this produces upward and return strokes in the upper zone of the letters: for instance, the upper part of a _t_. The second row passes _positive_ currents of equal strength with the negative, and influences the up-and-down strokes of the centre zone, _e.g._ those of _o_; the third row passes positive currents _twice_ as strong as the negative, and is responsible for double-length vertical strokes in the centre and lower zones, _e.g._ the stroke in _p_. In order that the record shall not be a series of zigzags it is necessary that the return strokes in the vertical elements shall be on the same path as the out strokes; and as the point of light is continuously tending to move from left to right of the paper there must at times be present a counteracting tendency counterbalancing it exactly, so that the path of the light point is purely vertical. At other times not merely must the horizontal movements balance each other, but the right-to-left element must be stronger than the left-to-right, so that strokes such as the left curve of an _e_ may be possible. To this end rows 4 and 5 of the perforations pass currents working the second telephone diaphragm, which moves the mirror on a vertical axis so that it reflects the ray horizontally. It will be noticed that the holes in rows 3, 4, 5 vary in size to permit the passage of currents during periods of different length. In this manner the little junction-hooks of such letters as _r_, _w_, _v_, _b_ are effected. As fast as the sensitised paper strip is covered with the movements of the dancing spot of light it is passed on over rollers through developing and fixing chemical baths; so that the receiving of messages is purely automatic. The reader can judge for himself the results of this ingenious system as shown in a short section of a message transmitted by Mr. Pollak. The words shown actually occupied two seconds in transmission. They are beautifully clear. It is said that by the aid of a special “multiplex” device thirty sets of Pollak-Virag apparatus can be used simultaneously on a line! The reader will be able, by the aid of a small calculation, to arrive at some interesting figures as regards their united output. THE TELEPHONE.