Here we are, then, living, in a sense on the top of the ages of human history, like the dwellers on a coral island. Hundreds of generations have toiled to raise the vast structure for us, like the little coral "polyps" which build their own lives into the mass, yet we take it all as a matter of course and rarely give a thought to the marvelous ways by which it has come about. You may have just glanced at your watch. To you, perhaps, a watch has always seemed merely a small mechanism which was bought in a store. That is true, and yet—remember this—the first manufacturer who had a hand in producing that watch for you, may have been a caveman. In order to appreciate this development, let us return, therefore, for another rapid view of prehistoric times; life in its crudest form—one day much like another—a scanty population, huddled in little groups in places naturally sheltered—the simplest physical needs to be provided for—little thought of the past or care for the future—time-reckoning reduced to the single thought of appointment—no reason for measuring intervals—in these and other respects antiquity presented the greatest possible contrast to our complicated modern life. The long-armed man of our first chapter noticed that as the sun moved, the shadows of the cliff also moved, as did all other shadows. As he formed habits of regularity, it was natural for him to perform a certain daily act when, perhaps, the shadow of a certain tree touched upon a certain stone. This would be a _natural_ sun-dial. But a thinner, sharper shadow would be easier to observe; suppose, therefore, that some successor to the long-armed man set up a pole in some open space and laid a stone to mark the spot where the shadow fell when the sun was highest in the heavens. That would be an _artificial_ sun-dial—_a device deliberately planned to accomplish a certain purpose_. The man who first took such a step was probably the first manufacturer who had a hand in supplying you with your watch. The shaggy mammoth, the terrible saber-tooth tiger and the eohippus, the small ancestor of our modern horse, must have been familiar sights when time-recording at the hands of some rude, unconscious inventor thus began the long story of its development. One stone reached by the moving shadow would mark only one point of time each day. Why not place two stones, three stones, or even more and get more markings? Such a procedure would be more useful because it would indicate the time of other happenings in the course of the day. The sun would pass across the skies and the shadow must travel around the pole. What more natural than to place the stones in a circle and get a series of these markings? Of course, as the ages passed, life became more complex—not complex as we would consider it to-day, but, as compared with its rude beginnings. New habits were formed, new needs developed, new activities were undertaken at different periods.