_Chromic Acid or Bichromate Battery._--This form of battery is very similar to Grove's, the difference being that, in the place of the nitric acid as the exciting liquid, either chromic acid, or a solution of bichromate of potash, sulphuric acid and water is substituted.
A form of this battery, as designed by Dr. Hertz, is used in connection with the German system of torpedo defence.
_Leclanché Voltaic Battery._--This form of Voltaic battery was invented by M. Leclanché, some twelve years ago. At Fig. 73 is shown a cell of this battery in its original form. The positive pole _a_ consists of a plate of graphite in a porous pot _b_, and surrounded by a mixture of peroxide of manganese and graphite. The negative pole _c_ is a rod or pencil of amalgamated zinc. The whole is enclosed in an outer vessel of glass _d_ containing a solution of sal ammoniac.
A modified form of the Leclanché cell as used in a firing battery is shown at Fig. 74. It consists of an ebonite trough or outer vessel _a_ about 16" long, 9" deep, and 2-3/4" wide. The negative pole or zinc plate _b_ is of similar shape to the trough _a_, but with its base removed, and does not fit the trough exactly, the space between it and the trough being left to ensure the former being completely surrounded by the sal ammoniac solution; the positive pole, or carbon element, consists of four gas carbon plates _c_ attached together at their head by means of lead, and enclosed in a flannel bag, in which they are firmly embedded in the peroxide of manganese mixture; the positive element is of such a shape that it fits loosely between the sides, and is nearly of the same height as the zinc plate.
The object of such a form of cell was to obtain an electric current of large _quantity_, with as few cells as possible, by which means the loss of power which might occur from the employment of a great number of small cells is avoided.
_Advantages of a Leclanché Firing Battery._--The advantages of the Leclanché firing battery are:--
1.--The absence of chemical action when the battery circuit is not complete, and consequently there is no waste of material.
3.--It may be kept ready for action in store without in any way deteriorating.