the acid and alkali found after its action upon water.
The same necessity that urged him to decide the doubtful point, which
interfered with the extension of his views, and destroyed the strictness of
his reasoning, has obliged me to ascertain the identity or difference of
common and voltaic electricity. I have satisfied myself that they are
identical, and I hope the experiments which I have to offer and the proofs
flowing from them, will be found worthy the attention of the Royal Society.

267. The various phenomena exhibited by electricity may, for the purposes
of comparison, be arranged under two heads; namely, those connected with
electricity of tension, and those belonging to electricity in motion. This
distinction is taken at present not as philosophical, but merely as
convenient. The effect of electricity of tension, at rest, is either
attraction or repulsion at sensible distances. The effects of electricity
in motion or electrical currents may be considered as 1st, Evolution of
heat; 2nd, Magnetism; 3rd, Chemical decomposition; 4th, Physiological
phenomena; 5th, Spark. It will be my object to compare electricities from
different sources, and especially common and voltaic electricities, by
their power of producing these effects.

I. _Voltaic Electricity._

268. _Tension._--When a voltaic battery of 100 pairs of plates has its
extremities examined by the ordinary electrometer, it is well known that
they are found positive and negative, the gold leaves at the same extremity
repelling each other, the gold leaves at different extremities attracting
each other, even when half an inch or more of air intervenes.

269. That ordinary electricity is discharged by points with facility
through air; that it is readily transmitted through highly rarefied air;
and also through heated air, as for instance a flame; is due to its high
tension. I sought, therefore, for similar effects in the discharge of
voltaic electricity, using as a test of the passage of the electricity
either the galvanometer or chemical action produced by the arrangement
hereafter to be described (312. 316.).

270. The voltaic battery I had at my disposal consisted of 140 pairs of
plates four inches square, with double coppers. It was insulated
throughout, and diverged a gold leaf electrometer about one third of an
inch. On endeavouring to discharge this battery by delicate points very
nicely arranged and approximated, either in the air or in an exhausted