uce mechanical motion.
[Footnote: See Helmholtz: 'Wechselwirkung der Naturkraefte.'] Here,
then, was the mine in which our gem must be sought. A modified and
more refined form of the ancient faith revived; and, for aught I know,
a remnant of sanguine designers may at the present moment be engaged
on the problem which like-minded men in former ages left unsolved.

And why should a perpetual motion, even under modern conditions, be
impossible? The answer to this question is the statement of that
great generalisation of modern science, which is known under the name
of the Conservation of Energy. This principle asserts that no power
can make its appearance in nature without an equivalent expenditure of
some other power; that natural agents are so related to each other as
to be mutually convertible, but that no new agency is created. Light
runs into heat; heat into electricity; electricity into magnetism;
magnetism into mechanical force; and mechanical force again into light
and heat. The Proteus changes, but he is ever the same; and his
changes in nature, supposing no miracle to supervene, are the
expression, not of spontaneity, but of physical necessity. A
perpetual motion, then, is deemed impossible, because it demands the
creation of energy, whereas the principle of Conservation is--no
creation, but infinite conversion.

It is an old remark that the law which moulds a tear also rounds a
planet. In the application of law in nature the terms great and small
are unknown. Thus the principle referred to teaches us that the
Italian wind, gliding over the crest of the Matterhorn, is as firmly
ruled as the earth in its orbital revolution round the sun; and that
the fall of its vapour into clouds is exactly as much a matter of
necessity as the return of the seasons. The dispersion, therefore, of
the slightest mist by the special volition of the Eternal, would be as
much a miracle as the rolling of the Rhone over the Grimsel
precipices, down the valley of Hash to Meyringen and Brientz.

It seems to me quite beyond the present power of science to
demonstrate that the Tyrolese priest, or his colleague of the Rhone
valley, asked for an 'impossibility' in praying for good weather; but
Science can demonstrate the incompleteness of the knowledge of nature
which limited their prayers to this narrow ground; and she may lessen
the number of instances in which we 'ask amiss,' by showing that we
sometimes pray for the performanc