[A] Many of the spaces in this table originally left blank may now be
filled. Thus with _thermo-electricity_, Botto made magnets and
obtained polar chemical decomposition: Antinori produced the spark;
and if it has not been done before, Mr. Watkins has recently heated a
wire in Harris's thermo-electrometer. In respect to _animal
electricity_, Matteucci and Linari have obtained the spark from the
torpedo, and I have recently procured it from the gymnotus: Dr. Davy
has observed the heating power of the current from the torpedo. I have
therefore filled up these spaces with crosses, in a different position
to the others originally in the table. There remain but five spaces
unmarked, two under _attraction_ and _repulsion_, and three under
_discharge by hot air_; and though these effects have not yet been
obtained, it is a necessary conclusion that they must be possible,
since the _spark_ corresponding to them has been procured. For when a
discharge across cold air can occur, that intensity which is the only
essential additional requisite for the other effects must be
present.--_Dec. 13 1838._

S 8. _Relation by Measure of common and voltaic Electricity._[A]

[A] In further illustration of this subject see 855-873 in Series
VII.--_Dec. 1838._

361. Believing the point of identity to be satisfactorily established, I
next endeavoured to obtain a common measure, or a known relation as to
quantity, of the electricity excited by a machine, and that from a voltaic
pile; for the purpose not only of confirming their identity (378.), but
also of demonstrating certain general principles (366, 377, &c.), and
creating an extension of the means of investigating and applying the
chemical powers of this wonderful and subtile agent.

362. The first point to be determined was, whether the same absolute
quantity of ordinary electricity, sent through a galvanometer, under
different circumstances, would cause the same deflection of the needle. An
arbitrary scale was therefore attached to the galvanometer, each division
of which was equal to about 4 deg., and the instrument arranged as in former
experiments (296.). The machine (290.), battery (291.), and other parts of
the apparatus were brought into good order, and retained for the time as
nearly as possible in the same condition. The experiments were alternated
so as to indicate any change in the condition of the apparatus and supply
the necessary cor