the instinct of self-preservation. But this instinct in animals is soon
satisfied, whereas in human beings it has been leading ever onward
toward complete emancipation.

The progress of civilization is a long chain of countless achievements
each one of which has increased man's independence. Early man perhaps
did not conceive the idea of fire and then set out to produce it. His
infant mind did not operate in this manner. But when he accidentally
struck a spark, produced fire by friction, or discovered it in some
other manner, he saw its possibility. It is thrilling to picture
primitive man at his first bonfire, enjoying the warmth, or at least
interested in it. But how wonderful it must have become as twilight's
curtain was drawn across the heavens! This controllable fire emitted
_light_. It is easy to imagine primitive man pondering over this
phenomenon with his sluggish mind. Doubtless he cautiously picked up a
flaming stick and timidly explored the crowding darkness. Perhaps he
carried it into his cave and behold! night had retreated from his abode!
No longer was it necessary for him to retire to his bed of leaves when
daylight failed. The fire not only banished the chill of night but was a
power over darkness. Viewed from the standpoint of civilization, its
discovery was one of the greatest strides along the highway of human
progress. The activities of man were no longer bounded by sunrise and
sunset. The march of civilization had begun.

In the present age of abundant artificial light, with its manifold
light-sources and accessories which have made possible countless
applications of light, mankind does not realize the importance of this
comfort. Its wonderful convenience and omnipresence have resulted in
indifference toward it by mankind in general, notwithstanding the fact
that it is essential to man's most important and educative sense. By