Division of the Stars into Magnitudes—Division of 219-257 the Stars according to their Spectra—Stars Larger and Smaller than the Sun—The Distances of the Stars—Variable Stars—Double and Binary Stars—Spectroscopic Binaries and how they are Discovered—Proper Motions of the Stars—Number of the Stars—New, or Temporary Stars—The Milky Way—The Nebulæ—The Two Kinds of Nebulæ—Spiral Nebulæ—The Nebular Hypothesis—Applications of Photography to Stars and Nebulæ—The Constellations—How to Learn the Constellations—Their Antiquity—Description of the Principal Constellations Visible from the Northern Hemisphere at Various Times of the Year INDEX 259 ------------------------------------------------------------------------ ILLUSTRATIONS PAGE THE LUNAR “CRATER” COPERNICUS _Frontispiece_ PHOTOGRAPH OF SOUTH POLAR 8 REGION OF THE MOON THE MOON NEAR THE “CRATER” 20 TYCHO DRAWING OF JUPITER 28 DRAWING OF JUPITER 28 JUPITER 38 SATURN 46 SATURN 46 THE MILKY WAY ABOUT CHI CYGNI 58 THE GREAT SOUTHERN 64 STAR-CLUSTER IN CENTAURI PHOTOGRAPH OF A GROUP OF 76 SUN-SPOTS POLAR STREAMERS OF THE SUN, 89 ECLIPSE OF 1889 SOLAR CORONA AT THE ECLIPSE OF 89 1871 MOREHOUSE'S COMET, OCTOBER 15, 96 1908 MOREHOUSE'S COMET, NOVEMBER 96 15, 1908 HEAD OF THE GREAT COMET OF 105 1861 HALLEY'S COMET, MAY 5, 1910 105 THE SIX-TAILED COMET OF 1744 112 SPIRAL NEBULA IN URSA MAJOR (M 124 101) THE WHIRLPOOL NEBULA IN CANES 124 VENATICI TRESS NEBULA (N. G. C. 6992) 132 IN CYGNUS THE GREAT ANDROMEDA NEBULA 140 SPIRAL NEBULA IN CEPHEUS (H. 154 IV. 76) NEBULOUS GROUNDWORK IN TAURUS 154 NEBULA IN SAGITTARIUS (M. 8) 162 THE GREAT NEBULA IN ORION 180 PHOTOGRAPHS OF MARS 200 SCHIAPARRELLI’S CHART OF 220 MARTIAN “CANALS”