G. W. Hough on the Galvanic Battery. 183 
the instrument was effected by two methods, viz: by means of 
the divided current, and by the revolving disk. 
The Rheostat was constructed by winding No. 30 silk-cov- 
ered wire, around a wooden cylinder ten inches in circumfer- 
ence and 8 inches in length. The coils were separated in dif- 
ferent groups, and so connected with switches that any number 
could readily be introduced in the circuit. 
For measuring the comparative resistance of different liquids, 
two small platinum plates, attached to protected wires, were 
fastened to a block of wood, and maintained at a uniform dis- 
tance from each other, 
Daniell’s Battery—The battery originally constructed by 
Daniell consisted of a copper cylinder 6 inches high and 3$ 
inches in diameter, with a porous cell or ox-gullet passing 
through the center, in which was suspended a rod of zinc 6 
inches in length, and 3 inch in diameter, The porous cell pass- 
ed through the bottom of the copper cylinder and the end was 
connected with a glass siphon, bent in such a manner that the 
top was on a level with the surface of the liquid. The bat- 
tery was excited with a saturated solution of sulphate of cop- 
per and water acidulated with sulphuric acid. When fresh 
water and acid was poured in the top of the porous cell, an 
equal amount of liquid was forced out from the bottom through 
the siphon. It was intended by this arrangement to maintain 
at all times the same strength of acidulated water about the 
zinc. After this battery came in general use, porous clay cells 
were substituted for the membranous bag, and the siphon was 
iscarded. 
of the battery are joined s.z. is formed in the cell containing 
* The following abbreviations are used: g. Quantity of electricity flowing in 
the external circuit; s.c. sulphate of copper; s.2. sulphate of zine. 
