In Messrs. Barrier and Tourville’s Electrodock (Fig. 2) the plates are formed of concentric leaden tubes fixed into a wooden cover.  These tubes are threaded internally and externally, and the grooves thus produced are filled with a peculiar cement composed of litharge, powdered charcoal, and permanganate of potash, triturated together, sifted, and then mixed with glucose or sugar sirup so as to make a paste of them.  This mixture forms a cement that is very adhesive after, as well as before, the electrolytic action.

[Illustration:  FIG. 3.—­KORNBLUH’S ACCUMULATOR.]

In Kornbluh’s accumulators the plates consist of ribbed leaden gratings between which is compressed red lead prepared in a peculiar manner, and constituting, 48 hours after formation, a compact mass with the lead.  The tangs of the plates are widened so as to touch one another while leaving a proper distance between the plates themselves, and are hollowed out for the reception of a rod provided at its extremities with a winged nut and jam nut for passing them up close to one another.  The plates, properly so called, are held apart by rubber bauds.  The glass vessels are placed in osier baskets.—­La Lumiere Electrique.

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INDUSTRIAL MODEL OF THE REYNIER ZINC ACCUMULATOR.

The three models of a secondary battery that I recently made known to the readers of this journal have been the object of continuous experiment.  Conformably to the provisions of theory, the zinc accumulator has shown itself practically superior to the two others, and I have therefore chosen this type for getting up an industrial model, which is shown in the annexed cut.  The accumulator contains four Plante positives, having a wide surface, and three negatives constructed of smooth sheets of lead covered with zinc by the electrolysis of the acidulated solution of zinc sulphate in which the couple is immersed.  Accidental contact with the interior of the pile is prevented by glass tubes fixed to the negatives by means of leaden bands.  The seven electrodes are carried by as many distinct crosspieces of paraffined wood, which rest upon the edges of the trough and hold the plates at a certain distance from the bottom.  These various crosspieces, which touch one another, take the place of a cover.  Each plate is provided with a terminal.  The four positive terminals are all on the same side, and the three negatives are on the opposite side.  Two brass rods ending in a wire-clamp connect the respective terminals of the same name.  The trough consists of two oblong wooden receptacles, one within the other, and having a play of several millimeters.  This space is lined with a tight, elastic, insulating cement having tar for a base.

[Illustration:  REYNIER’S ZINC ACCUMULATOR. (One-fifth actual size.)]

The careful insulation of the trough and all parts of the apparatus, and the purity of the metal and its amalgamation, reduce the local attack of the zinc to almost nothing.  So the coefficient of restitution is now comparable with that of accumulators of the Plante type.