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 extinguishing the light and pondering upon his helplessness in the resulting darkness, man may gain an idea of its overwhelming importance.  Those unfortunate persons who suffer the terrible calamity of blindness after years of dependence upon sight will testify in heartrending terms to the importance of light.  Milton, whose eyesight had failed, laments,

    O first created beam and thou great Word
    “Let there be light,” and light was over all,
    Why am I thus bereaved thy prime decree?

Perhaps only through a similar loss would one fully appreciate the tremendous importance of light to him, but imagination should be capable of convincing him that it is one of the most essential and pleasure-giving phenomena known to mankind.

A retrospective view down the vista of centuries reveals by contrast the complexity with which artificial light is woven into human activities of the present time.  Written history fails long before the primitive races are reached, but it is safe to trust the imagination to penetrate the fog of unwritten history and find early man huddled in his cave as daylight wanes.  Impelled by the restless spirit of progress, this primitive being grasped the opportunity which fire afforded to extend his activities beyond the boundaries of daylight.  The crude art upon the walls of his cave was executed by the flame of a smoking fagot.  The fire on the ledge at the entrance to his abode became a symbol of home, as the fire on the hearth has symbolized home and hospitality throughout succeeding ages.  The accompanying light and the protection from cold combined to establish the home circle.  The ties of mated animals expanded through these influences to the bonds of family.  Thus light was woven early into family life and has been throughout the ages a moralizing and civilizing influence.  To-day the residence functions as a home mainly under artificial light, for owing to the conditions of living and working, the family group gathers chiefly after daylight has failed.

From the pine knot of primitive man to the wonderfully convenient light-sources of to-day there is a great interval, consisting, as appears retrospectively, of small and simple steps long periods apart.  Measured by present standards and achievements, development was slow at first and modern man may be inclined to impatience as he views the history of light and human progress.  But the achievements of early centuries, which appear so simple at the present time, were really great accomplishments when considered in the light