of knowledge and the joy of
the discovery of the causes of things sung by the old poets--the
supreme delight of extending the realm of law and order ever farther
towards the unattainable goals of the infinitely great and the
infinitely small, between which our little race of life is run. In the
course of this work, the physical philosopher, sometimes
intentionally, much more often unintentionally, lights upon something
which proves to be of practical value. Great is the rejoicing of those
who are benefited thereby; and, for the moment, science is the Diana
of all the craftsmen. But, even while the cries of jubilation resound
and this floatsam and jetsam of the tide of investigation is being
turned into the wages of workmen and the wealth of capitalists, the
crest of the wave of scientific investigation is far away on its
course over the illimitable ocean of the unknown.

[Sidenote: It is in its turn assisted by industrial improvements.]

Far be it from me to depreciate the value of the gifts of science to
practical life, or to cast a doubt upon the propriety of the course of
action of those who follow science in the hope of finding wealth
alongside truth, or even wealth alone. Such a profession is as
respectable as any other. And quite as little do I desire to ignore
the fact that, if industry owes a heavy debt to science, it has
largely repaid the loan by the important aid which it has, in its
turn, rendered to the advancement of science. In considering the
causes which hindered the progress of physical knowledge in the
schools of Athens and of Alexandria, it has often struck me[A] that
where the Greeks did wonders was in just those branches of science,
such as geometry, astronomy, and anatomy, which are susceptible of
very considerable development without any, or any but the simplest,
appliances. It is a curious speculation to think what would have
become of modern physical science if glass and alcohol had not been
easily obtainable; and if the gradual perfection of mechanical skill
for industrial ends had not enabled investigators to obtain, at
comparatively little cost, microscopes, telescopes, and all the
exquisitely delicate apparatus for determining weight and measure and
for estimating the lapse of time with exactness, which they now
command. If science has rendered the colossal development of modern
industry possible, beyond a doubt industry has done no less for modern
physics and chemistry, and for a great d