Owing to some unaccountable variations in the change of the lever or needle, M. Baille was obliged to measure the change at each observation. This was done by joining the + pole of the battery to the needle, and one pair of the fixed balls, and observing the deflection; then the deflection produced by the other balls was observed. This operation was repeated several times.
The battery, X, to be measured consisted of ten similar elements, and one pole of it was connected to the fixed balls, while the other pole was connected to the earth. The needle, of course, remained in contact with the + pole of the charging battery, P.
The deflections were read from a clear glass scale, placed at a distance of 3.30 meters from the needle, and the results worked out from Coulomb's static formula,
, with
In M. Baillie's experiments, O = 437³, and Σpr²= 32171.6 (centimeter grammes), the needle having been constructed of a geometrical form.
The following numbers represent the potential of an element of the battery--that is to say, the quantity of electricity that the pole of that battery spreads upon a sphere of one centimeter radius. They are expressed in units of electricity, the unit being the quantity of electricity which, acting upon a similar unit at a distance of one centimeter, produces a repulsion equal to one gramme:
Volta pile 0.03415 open circuit.
Zinc, sulphate of copper, copper 0.02997 "
Zinc, acidulated water, copper, sulphate of copper 0.03709 "
Zinc, salt water, carbon peroxide of manganese 0.05282 "
Zinc, salt water, platinum, chloride of platinum 0.05027 "
Zinc, acidulated water, carbon nitric acid 0.06285 "
These results were obtained just upon charging the batteries, and are, therefore, slightly higher than the potentials given after the batteries became older. The sulphate of copper cells kept about their maximum value longest, but they showed variations of about 10 per cent.