The best possible manner by which to restore partially the strength of a dry battery is to proceed as follows: Bore several small holes with a 1/4-inch bit around the carbon of a battery, to within an inch of the bottom. Fill these holes to within 1/2 inch of the top with water, and the remaining 1/2 inch with paraffine, or better still, sealing wax. The writer has taken a cell that was in such a worn-out state as to barely "flicker" a tangent galvanometer, and subjected it to this process, after which it read and easily maintained five amperes.

A battery can be made by filling a crock with a saturated solution of the chemicals of a dry cell with water. Bundles of carbon and zinc are placed on this solution for the + and - poles. This battery is especially adapted for closed-circuit work.