conspicuous of the heavenly objects. Its name means "the Measurer of Time." As our first ancestors perceived, the moon seemed to have the strange property of changing shape; sometimes it was a brilliant disk; sometimes a crescent; sometimes it failed to appear at all. These changes occurred over and over again—always in the same order, and the same number of days apart. What, then, could be more convenient than for the men inhabiting neighboring valleys to agree to meet at a certain spot, with arms and with several days' provisions, at the time of the next full moon?—moonlight being also propitious for a night attack.

For this and other reasons, the moon was added to the sun as a human timepiece, and man began to show his mental resources—he was able to plan ahead. Note, however, that he was not concerned with measuring the passage of time, but merely with fixing upon a future date; it was not a question of how long but of when.

This presumptuous, two-legged fighting animal, from whom we are descended, and many of whose instincts we still retain, began to enlarge his warfare, and thereby to improve his organization. For the sake of his own safety, he learned to combine with his fellows, finding strength in numbers, like the wolves in the pack; or, like ants and bees, finding in the combined efforts of many a means of gaining for each individual more food and better shelter than he could win for himself alone.

For example, it was possible that a neighboring tribe, instead of waiting to be attacked, was planning an attack upon its own account. It would not do to be surprised at night. Sentries must be established to keep watch while others slept, and to waken their comrades in case of need. Our very word "watch" is derived from the old Anglo-Saxon word "waeccan," meaning "wake." And yet people who tried to watch for long at a stretch would be apt to doze. They must be relieved at regular times; it was a matter of necessity, but how could one measure time at night?

Where man has been confronted with a pressing problem he has generally found its solution. Probably in this case the stars gave him a clue. If the sky were clear, their positions would help to divide the night into "watches" of convenient length.

Thus did primitive man begin to study the skies. No longer a mere animal, he was beginning, quite unconsciously, to give indications of becoming a student.