CHAPTER XII

STARS AND NEBULÆ

Stellar Chemistry--Four Orders of Stars--Their Relative Ages--Gaseous Stars--Spectroscopic Star-Catalogues--Stellar Chemistry--Hydrogen Spectrum in Stars--The Draper Catalogue--Velocities of Stars in Line of Sight--Spectroscopic Binaries--Eclipses of Algol--Catalogues of Variables--New Stars--Outbursts in Nebulæ--Nova Aurigæ--Nova Persei--Gaseous Nebulæ--Variable Nebulæ--Movements of Nebulæ--Stellar and Nebular Photography--Nebulæ in the Pleiades--Photographic Star-charting--Stellar Parallax--Double Stars--Stellar Photometry--Status of Nebulæ--Photographs and Drawings of the Milky Way--Star Drift 372

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