LICK OBSERVATORY, MOUNT HAMILTON, CALIFORNIA 129 PHOTOGRAPHING WITH THE 40-INCH REFRACTOR 129 GREAT SUNSPOT GROUP OF AUGUST 8, 1917 160 CALCIUM FLOCCULI ON THE SUN 161 ECLIPSE OF THE MOON, WITH THE LUNAR SURFACE VISIBLE 161 MOON'S SURFACE IN THE REGION OF COPERNICUS 192 SOUTH CENTRAL PORTION OF THE MOON, AT LAST QUARTER 193 CORONA OF THE SUN DURING AN ECLIPSE 224 VENUS, IN THE CRESCENT PHASE 225 MARS, SHOWING BRIGHT POLAR CAP 225 JUPITER, THE GIANT PLANET 256 NEPTUNE AND ITS SATELLITES 256 SATURN, WITH EDGE OF RINGS ONLY IN VIEW 257 SATURN, WITH RINGS DISPLAYED TO FULLEST EXTENT 257 TWO VIEWS OF HALLEY'S COMET 288 SWIFT'S COMET, WHICH SHOWED REMARKABLE TRANSFORMATIONS 288 METEOR TRAIL IN FIELD WITH FINE NEBULÆ 289 RING NEBULA IN LYRA 320 DUMB-BELL NEBULA 321 STAR CLOUDS AND BLACK HOLES IN SAGITTARIUS 352 GREAT NEBULA IN ANDROMEDA 353 CHAPTER I ASTRONOMY A LIVING SCIENCE Like life itself we do not know when astronomy began; we cannot conceive a time when it was not. Man of the early stone age must have begun to observe sun, moon, and stars, because all the bodies of the cosmos were there, then as now. With his intellectual birth astronomy was born. Onward through the childhood of the race he began to think on the things he observed, to make crude records of times and seasons; the Chaldeans and Chinese began each their own system of astronomy, the causes of things and the reasons underlying phenomena began to attract attention, and astronomy was cultivated not for its own sake, but because of its practical utility in supplying the data necessary to accurate astrological prediction. Belief in astrology was universal. The earth set in the midst of the wonders of the sky was the reason for it all. Clearly the earth was created for humanity; so, too, the heavens were created for the edification of the race. All was subservient to man; naturally all was geocentric, or earth-centered. From the savage who could count only to five, the digits of one hand, civilized man very slowly began to evolve; he noted the progress of the seasons; the old records of eclipses showed Thales, an early Greek, how to predict their happenings, and true science had its birth when man acquired the power to make forecasts that always came true.