Comet of 1889--Swift's Comet of 1892--Origin of Comets 345

CHAPTER XII

STARS AND NEBULAE

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 Nebulae--Nova Aurigae--Nova
Persei--Gaseous Nebulae--Variable Nebulae--Movements of Nebulae--Stellar
and Nebular Photography--Nebulae in the Pleiades--Photographic
Star-charting--Stellar Parallax--Double Stars--Stellar
Photometry--Status of Nebulae--Photographs and Drawings of the Milky
Way--Star Drift 372

CHAPTER XIII

METHODS OF RESEARCH

Development of Telescopic Power--Silvered Glass Reflectors--Giant
Refractors--Comparison with Reflectors--The Yerkes
Telescope--Atmospheric Disturbance--The Lick Observatory--Mechanical
Difficulties--The Equatoreal _Coude_--The Photographic
Camera--Retrospect and Conclusion 428

APPENDIX

Chronology, 1774-1893--Chemical Elements in the Sun (Rowland,
1891)--Epochs of Sun-spot Maximum and Minimum from 1610 to
1901--Movements of Sun and Stars--List of Great Telescopes--List of
Observatories employed in the Construction of the Photographic Chart
and Catalogue of the Heavens 443

INDEX 471

LIST OF ILLUSTRATIONS

Photograph of the Great Nebula in Orion, 1883 _Frontispiece_

Photographs of Jupiter, 1879, and of Saturn, 1885 _Vignette_

Plate I. Photographs of the Solar Chromosphere
and Prominences _To face p. 198_

Plate II. Photograph of the Great Comet of May,
1901 (Taken at the Royal Observatory, Cape
of Good Hope) " 343

Plate III. The Great Comet of September, 1882
(Photographed at the Cape of Good Hope) " 359

Plate IV. Photographs of Swift's Comet, 1892 " 368

Plate V. Photographic and Visual Spectrum of