It is early morning. The soft, red sandstone cliffs are bathed in the golden glow of dawn. As the great sun climbs higher in the eastern sky, the sharply outlined shadow of the opposite cliff descends slowly along the western wall of the narrow canyon. A shaggy head appears from an opening, half-way up the cliff, and is followed by the grotesque, stooping figure of a long-armed man, hairy and nearly naked, save for a girdle of skins. He grasps a short, thick stick, to one end of which a sharpened stone has been bound by many crossing thongs, and, without a word, he makes his way down among the bushes and stones toward the bed of the creek. Another head appears at the same opening in the cliff—that of a brown-skinned woman with high cheek-bones, a flat nose, and tangled hair. She shouts after the retreating form of the man, and he stops, and turns abruptly. Then he points to the edge of the shadow far above his, and, with a sweeping gesture, indicates a large angular rock lying in the bed of the stream near by. Apparently understanding the woman nods and the man soon disappears into the brush. The forenoon wears along, and the line of shadow creeps down the face of the canyon wall until it falls at last across the angular rock against which the dashing waters of the stream are breaking. The woman who has been moving about near the cave opening begins to look expectant and to cast quick glances up and down the canyon. Presently the rattle of stones caught her ear and she sees the long-armed man picking his way down a steep trail. He still carries his stone-headed club in one hand, while from the other there swings by the tail the body of a small, furry animal. Her eyes flash hungrily, and she shows her strong, white teeth in a grin of anticipation. [Illustration: THE CAVE MAN AND THE MOVING SHADOW _"I'll be back when the shadow touches that stone." It was by such crude expedients that our primitive ancestors timed their engagements._] Perhaps it has not been hard to follow the meaning of this little drama of primitive human need. Our own needs are not so very different, even in this day, although our manners and methods have somewhat changed since the time of the caveman. Like ourselves, this savage pair awoke with sharpened appetite, but, unlike ourselves, they had neither pantry nor grocery store to supply them. Their meal-to-be, which was looking for its own breakfast among the rocks and trees, must be found and killed for the superior needs of mankind, and the hungry woman had called after her mate in order to learn when he expected to return. No timepieces were available, but that great timepiece of nature, the sun, by which we still test the accuracy of our clocks and watches, and a shadow falling upon a certain stone, served the need of this primitive cave-dweller in making and keeping an appointment.