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