Page:Motors and motor-driving (1902).djvu/323

Rh The first step in the process of manufacture of the plate depicted in fig. 8 consists of mounting a sheet of thin pure lead, perforated in the manner shown, in a heated mould, in which a raised edge undercut at the sides is cast on to it, together with the lug or connecting piece projecting from the top of the plate. The grid thus constructed is smeared level with a paste mainly composed of ground litharge moistened with dilute

sulphuric acid. The paste contains other things also. After smearing, the plate is dried in a warm room until the paste is thoroughly dry and hard, and the plate is then mounted with several others in a forming vessel of dilute sulphuric acid, in which it is connected to the negative pole of a battery of accumulators or a dynamo. The action of the current finally reduces the litharge to the condition of porous metallic lead, and the plate is then a negative, suitable for being assembled with other plates to form a battery cell. The positive consists of somewhat thicker plates, similarly formed as negatives in the manner described, and then connected to the positive of a forming battery or dynamo till all the porous lead is changed into lead peroxide, when the plate has become a positive. Each of the plates, whether positive or negative, is covered over as shown in fig. 8 by a grille of ebonite, which assists in maintaining the actual material in position, and also serves to keep the plates apart. A number of positive