Voltaic Electricity 5

air between the charcoal terminations of the poles of a powerful
battery, when they are gradually separated after contact.
Then the passage is through heated air exactly as with common
electricity, and Sir H. Davy has recorded that witli the original
battery of the Royal Institution this discharge passed through
a space of at least four inches.1 In the exhausted receiver the
electricity would strike through nearly half an inch of space,
and the combined effects of rarefaction and heat was such
upon the inclosed air as to enable it to conduct the electricity
through a space of six or seven inches.

11. The instantaneous charge of a Leyden battery by the
poles of a voltaic apparatus is another proof of the tension, and
also the quantity, of electricity evolved by the latter. Sir II.
Davy says,2 " When the two conductors from the ends of the
combination were connected with a Leyden battery, one with
the internal, the other with the external coating, the battery
instantly became charged; and on removing the wires and
making the proper connections, either a shock or a spark coul< 1
be perceived: and the least possible time of contact was sufficient.
to renew the charge to its full intensity."

12. In motion : i. Evolution of heat.—The evolution of heal
in wires and fluids by the voltaic current is matter of general
notoriety.

13. ii. Magnetism.—No fact is better known to philosophers
than the power of the voltaic current to deflect the magnetir
needle, and to make magnets according to certain laws; and no
effect can be more distinctive of an electrical current.

14. iii. Chemical decomposition.—The chemical powers of the
voltaic current, and their subjection to certain laws, are also
perfectly well known.

15. iv. Physiological effects.—The. power of the voltaic
current, when strong, to shock and convulse the whole animal
system, and when weak to affect the tongue and the eyes, is
very characteristic, jj

_i6. v. Spark.—-The brilliant star of light produced by the
discharge of a voltaic battery is known to all as the most
beautiful light that man can produce by art.

17. That these effects may be almost infinitely varied, some

being exalted whilst others arc diminished,, is universally ae-

knowledged; and yet without any doubt'of the identity of

character of the voltaic currents thus made to differ in their

1 Elements of Chemical Philosophy. '-' Hiii