The accompanying figure shows a series of four vats arranged one above another, in order to permit the water to circulate. Here _i_ and _h_ represent the plates connected with the poles of the dynamo through the conductors, _f_ and _g_; _m_ represents the porous partition; L, the spaces filled with sugar; and _l_, the compartments in which the water circulates.--_La Lumiere Electrique._ * * * * * [THE ELECTRICIAN.] A CURRENT METER. We give a description of a meter we made in June, 1883. You will find a cross section of the meter and also a printed dial we had made at the time. We called it an ampere register, but no doubt we would give it a better name to-day. The meter consisted of a glass tube, _c_, both ends of which were fitted into two bent pieces of piping, D and F, as shown. Through these bent tubes, D and F, passed the wires, a and _b_, which were connected to the binding posts, A and B. The part of the wire where it passed into the tubes was well insulated. At the ends, _a'_ and _b'_, was connected the coil, R, which consisted simply of a few turns of copper wire whose diameter was less than the leading wires, _a_ and _b_. To the tube, D, was attached a square tube, E, which had a little opening at the top so as to permit a small undershot wheel, I, to revolve freely. This undershot wheel was well pivoted and constructed very light. To the axis of this wheel was connected another system of wheels with indicators, as shown, J. Now the tubes, E and F, were connected to a reservoir, G. This reservoir consisted of a square tank, in the inside of which were soldered in an alternating manner square sheets of copper as shown in the drawing, _g_ _g'_ _g''_ _g'''_ ... These sheets acted as diffusers. These plates or sheets presented a very large surface. On the outside of the tank, G, were also diffusers, _h_ _h'_ ... arranged all round and presenting an appearance as if two books were open so as to form a square with their covers, the leaves being the diffusers. The diffusers on the outside were at right angles to those inside. [Illustration: CROSS SECTION OF JEHL AND RUPP'S CURRENT METER.]