y in setting something burning; whereby not the fuel
but the air was consumed, whereby also a most powerful radiation was
produced, in the waste waves of which we were content to sit stewing,
for the sake of the minute--almost infinitesimal--fraction of it which
enabled us to see.

Every one knows now, however, that combustion is not a pleasant or
healthy mode of obtaining light; but every one does not realize that
neither is incandescence a satisfactory and unwasteful method which is
likely to be practiced for more than a few decades, or perhaps a
century.

Look at the furnaces and boilers of a great steam engine driving a
group of dynamos, and estimate the energy expended; and then look at
the incandescent filaments of the lamps excited by them, and estimate
how much of their radiated energy is of real service to the eye. It
will be as the energy of a pitch pipe to an entire orchestra.

It is not too much to say that a boy turning a handle could, if his
energy were properly directed, produce quite as much real light as is
produced by all this mass of mechanism and consumption of material.
There might, perhaps, be something contrary to the laws of nature in
thus hoping to get and utilize some specific kind of radiation without
the rest, but Lord Rayleigh has shown in a short communication to the
British Association at York that it is not so, and that, therefore, we
have a right to try to do it.

We do not yet know how, it is true, but it is one of the things we
have got to learn.

Any one looking at a common glow-worm must be struck with the fact
that not by ordinary combustion, nor yet on the steam engine and
dynamo principle, is that easy light produced. Very little waste
radiation is there from phosphorescent things in general. Light of the
kind able to affect the retina is directly emitted; and for this, for
even a large supply of this, a modicum of energy suffices.

Solar radiation consists of waves of all sizes, it is true; but then
solar radiation has innumerable things to do besides making things
visible. The whole of its energy is useful. In artificial lighting
nothing but light is desired; when heat is wanted it is best obtained
separately by combustion. And so soon as we clearly recognize that
light is an electric vibration, so soon shall we begin to beat about
for some mode of exciting and maintaining an electrical vibration of
any required degree of rapidity. When this has been accomplished the
pro