swinging either from right to left or left to right: it was equal to
seventeen beats of my watch, the latter giving one hundred and fifty in a
minute. The object of these preparations was to arrange a voltaic
apparatus, which, by immersion in a given acid for a given time, much less
than that required by the needle to swing in one direction, should give
equal deflection to the instrument with the discharge of ordinary
electricity from the battery (363. 364.); and a new part of the zinc wire
having been brought into position with the platina, the comparative
experiments were made.

370. On plunging the zinc and platina wires five eighths of an inch deep
into the acid, and retaining them there for eight beats of the watch,
(after which they were quickly withdrawn,) the needle was deflected, and
continued to advance in the same direction some time after the voltaic
apparatus had been removed from the acid. It attained the five-and-a-half
division, and then returned swinging an equal distance on the other side.
This experiment was repeated many times, and always with the same result.

371. Hence, as an approximation, and judging from _magnetic force_ only at
present (376.), it would appear that two wires, one of platina and one of
zinc, each one eighteenth of an inch in diameter, placed five sixteenths of
an inch apart and immersed to the depth of five eighths of an inch in acid,
consisting of one drop oil of vitriol and four ounces distilled water, at a
temperature about 60°, and connected at the other extremities by a copper
wire eighteen feet long and one eighteenth of an inch thick (being the wire
of the galvanometer coils), yield as much electricity in eight beats of my
watch, or in 8/150ths of a minute, as the electrical battery charged by
thirty turns of the large machine, in excellent order (363. 364.).
Notwithstanding this apparently enormous disproportion, the results are
perfectly in harmony with those effects which are known to be produced by