XVI. THE ELECTRIC LIGHT.

[Footnote: A discourse delivered at the Royal Institution of Great
Britain on Friday, January 17, 1879, and introduced here as the latest
Fragment.]

THE subject of this evening's discourse was proposed by our late
honorary secretary. [Footnote: Mr. William Spottiswoode, now President
of the Royal Society] That word 'late' has for me its own
connotations. It implies, among other things, the loss of a comrade
by whose side I have worked for thirteen years. On the other hand,
regret is not without its opposite in the feeling with which I have
seen him rise by sheer intrinsic merit, moral and intellectual, to the
highest official position which it is in the power of English science
to bestow. Well, he, whose constant desire and practice were to
promote the interests and extend the usefulness of this institution,
thought that at a time when the electric light occupied so much of
public attention, a few sound notions regarding it, on the more purely
scientific side, might, to use his own pithy expression, be 'planted'
in the public mind. I am here to-night with the view of trying, to
the best of my ability, to realise the idea of our friend.

In the year 1800, Volta announced his immortal discovery of the pile.
Whetted to eagerness by the previous conflict between him and Galvani,
the scientific men of the age flung themselves with ardour upon the
new discovery, repeating Volta's experiments, and extending them in
many ways. The light and heat of the voltaic circuit attracted marked
attention, and in the innumerable tests and trials to which this
question was subjected, the utility of platinum and charcoal as means
of exalting the light was on all hands recognised. Mr. Children, with
a battery surpassing in strength all its predecessors, fused platinum
wires eighteen inches long, while 'points of charcoal produced a light
so vivid that the sunshine, compared with it, appeared feeble.'
[Footnote: Davy, 'Chemical Philosophy,' p. 110.] Such effects
reached their culmination when, in 1808, through the liberality of a
few members of the Royal Institution, Davy was enabled to construct a
battery of two thousand pairs of plates, with which he afterwards
obtained calorific and luminous effects far transcending anything
previously observed. The arc of flame between the carbon terminals
was four inches long, and by its heat quartz, sapphire, magnesia, and
lime, were melted like wax in a candle f