This apparatus has been also employed under some circumstances for producing an electric light and charging accumulators; but such applications are without economic interest, seeing the enormous consumption of sulphate of copper during the operation of the pile. The use of the apparatus is only truly effective in cases where it is necessary to have, before everything else, an energetic and exceedingly constant current.--_La Nature_. * * * * * SIEMENS' TELEMETER The accompanying cut illustrates a telemeter which was exhibited at the Paris Exhibition of Electricity, and which is particularly interesting from the fact that it is the first apparatus of this kind. It will be remembered that the object of a telemeter is to make known at any moment whatever the distance of a movable object, and that, too, by a direct reading and without any calculation. In Mr. Siemens' apparatus the problem is solved in the following manner: The movable object (very often a vessel) is sighted from two different stations--two points of the coast, for example--by two different observers. The sighting is done with two telescopes, A1 and A2, which the observers revolve around a vertical axis by means of two winches, K1 and K2, that gear with two trains of clockwork. There is thus constantly formed a large triangle, having for its apices the movable point sighted and the vertical axes, A1 and A2, of the two telescopes. On another hand, at a point situated between the two telescopes, there is a table, T T, that carries two alidades, a1v1, and a2v2, movable around their vertical axes, a1 and a2. The line, a1 a2, that joins these axes is parallel with that which joins the axes of the two telescopes; and the alidades are connected electrically with the telescopes by a system such that each alidade always moves parallel with the telescope that corresponds to it. It follows from this that the small triangle that has for apices, a1 a2, and the crossing point of the two alidades will always be like the large triangle formed by the line that joins the telescopes and the two lines of vision. If, then, we know the ratio of a1, a2 to A1 A2, it will suffice to measure on one of the alidades the distance from its axis to the point of crossing in order to know the distance from the movable object to the axis of the corresponding telescope. If the table, T T, be covered with a chart giving the space over which the ship is moving, so that a1 and a2 shall coincide with the points which A1 and A2 represent, the crossing of the threads of the alidades will permit of following on the chart all the ship's movements. In this way there maybe had a powerful auxiliary in coast defence; for all the points at which torpedoes have been sunk may be marked on the chart, and, as soon as the operator at the table finds, by the motion of the alidades, that the ship under observation is directly over a torpedo, he will be able to fire the latter and blow the enemy up.