water and the chloride were broken up in proportions expressed
by their respective equivalents. The amount of electric force which
wrenched asunder the constituents of the molecule of water was
competent, and neither more nor less than competent, to wrench asunder
the constituents of the molecules of the chloride of tin. The fact
is typical. With the indications of his voltameter he compared the
decompositions of other substances, both singly and in series. He
submitted his conclusions to numberless tests. He purposely introduced
secondary actions. He endeavoured to hamper the fulfilment of those laws
which it was the intense desire of his mind to see established. But
from all these difficulties emerged the golden truth, that under every
variety of circumstances the decompositions of the voltaic current are
as definite in their character as those chemical combinations which gave
birth to the atomic theory. This law of Electro-chemical Decomposition
ranks, in point of importance, with that of Definite Combining
Proportions in chemistry.

Footnotes to Chapter 6

[1] I copy these words from the printed abstract of a Friday
evening lecture, given by myself, because they remind me of
Faraday's voice, responding to the utterance by an emphatic
'hear! hear!'--Proceedings of the Royal Institution, vol.
ii. p. 132.

[2] In 1838 he expresses himself thus:--'The word current is
so expressive in common language that when applied in the
consideration of electrical phenomena, we can hardly divest
it sufficiently of its meaning, or prevent our minds from
being prejudiced by it.'--Exp. Resear., vol. i. p. 515. ($
1617.)

[3] This conclusion needs qualification. Faraday overlooked
the part played by ozone.

Chapter 7.

Origin of power in the voltaic pile.

In one of the public areas of the town of Como stands a statue with no
inscription on its pedestal, save that of a single name, 'Volta.' The
bearer of that name occupies a place for ever memorable in the history
of science. To him we owe the discovery of the voltaic pile, to which
for a brief interval we must now turn our attention.

The objects of scientific thought being the passionless laws and
phenomena of external nature, one might suppose that their investigation
and discussion would be completely withdrawn from the region of the
feelings, and pursued by the cold dry light of the intellect