Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

layers ; while between every pair, or two such leaves, there may also be placed a blank sheet of the paper, and thus hundreds, or even thousands, may be built up to compose the dry pile. But the paper evidently gathers a minutia of moisture from the at- mosphere, and this is the acting agent. This pile, being built upon an insulator, terminates at its top and bottom with the op- posite kinds of metals; the tin is the negative pole, while the manganese is the positive pole. This pile cannot yield any very appreciable current, and yet it will for years give small sparks between its poles at any time. This shows its peculiar polarity, or tendency to accumulate tension electricity at its extremities or poles. In 1836, Daniell conceived the idea of trying various durable partitions to separate the two liquids, as Becquerel had been trying to do. He placed the copper of each pair in a solution of the sulphate of copper, which occupied the larger outer space in the jar, while the zinc was placed in a solution of salt and water, or acidulated water — say sulphuric acid one part, to water twenty parts, or in sea water. He made some diaphragms with felt, some of stout paper, others of very thin wood. Expe- rience gives the preference for a kind of porous porcelain, that is durable and yet slowly transmits the liquids for action upon the metals. In the inner cell, then, — that is, within the porous cell, — he places the zinc in a solution of salt and water, or acidulated water; but the zinc is first coated with quick- silver, which prevents its being attacked ivJiHe the poles are not united by a con- ductor, and so with- out diminishing the effect of the battery while not in use 10 Pig. 10. A Series of three Daniell's Batteries for Galvanism, showing their Connections. But it will be perceived