Page:Popular Science Monthly Volume 38.djvu/375

Rh higher oxide, and on the other plate transformed into metallic sponge. This idea of Faure was an excellent one, and is at the foundation of the construction of all the commercial lead accumulators. The percentage of energy recovered by discharge was greatly increased. His method of keeping the paste in place by felts was, however, soon abandoned, because fine lead needles soon filled up the interstices of the felt, and thus made a metallic connection between the electrodes. Holes were then punched in the lead plates and the paste pressed into them. A large number of the patents recently issued for accumulators refer to methods of making these holes and pressing in the paste, or to the shape of the holes themselves after they have been punched. The shapes vary from a slight depression on the surface to a hole completely



through the plate, and even further, to a hollow plate, with small openings leading to the surface. A great deal depends upon this shape, for the paste changes its volume during the process of charging and discharging, the same as the metallic lead does, and it would tend to loosen itself from some shaped openings and fall to the bottom of the cell, while in others it would tend to tighten itself, and thus provide a better contact.