The illustrations contained in the present work are worthy of as careful study as is the text, and many of them are intended as an aid to experimental work and accurate measurement, e. g., the star maps, the diagrams of the planetary orbits, pictures of the moon, sun, etc. If the school possesses a projection lantern, a set of astronomical slides to be used in connection with it may be made of great advantage, if the pictures are studied as an auxiliary to Nature. Mere display and scenic effect are of little value.
A brief bibliography of popular literature upon astronomy may be found at the end of this book, and it will be well if at least a part of these works can be placed in the school library and systematically used for supplementary reading. An added interest may be given to the study if one or more of the popular periodicals which deal with astronomy are taken regularly by the school and kept within easy reach of the students. From time to time the teacher may well assign topics treated in these periodicals to be read by individual students and presented to the class in the form of an essay.
The author is under obligations to many of his professional friends who have contributed illustrative matter for his text, and his thanks are in an especial manner due to the editors of the Astrophysical Journal, Astronomy and Astrophysics, and Popular Astronomy for permission to reproduce here plates which have appeared in those periodicals, and to Dr. Charles Boynton, who has kindly read and criticised the proofs.
George C. Comstock.
University of Wisconsin, February, 1901.
CONTENTS
| CHAPTER | PAGE |
| [I.—Different kinds of measurement] | [1] |
| The measurement of angles and time. | |
| [II.—The stars and their diurnal motion] | [10] |
| Finding the stars—Their apparent motion—Latitude—Direction of the meridian—Sidereal time—Definitions. | |
| [III.—Fixed and wandering stars] | [29] |
| Apparent motion of the sun, moon, and planets—Orbits of the planets—How to find the planets. | |
| [IV.—Celestial mechanics] | [46] |
| Kepler's laws—Newton's laws of motion—The law of gravitation—Orbital motion—Perturbations—Masses of the planets—Discovery of Neptune—The tides. | |
| [V.—The earth as a planet] | [70] |
| Size—Mass—Precession—The warming of the earth—The atmosphere—Twilight. | |
| [VI.—The measurement of time] | [86] |
| Solar and sidereal time—Longitude—The calendar—Chronology. | |
| [VII.—Eclipses] | [101] |
| Their cause and nature—Eclipse limits—Eclipse maps—Recurrence and prediction of eclipses. | |
| [VIII.—Instruments and the principles involved in their use] | [121] |
| The clock—Radiant energy—Mirrors and lenses—The telescope—Camera—Spectroscope—Principles of spectrum analysis. | |
| [IX.—The moon] | [150] |
| Numerical data—Phases—Motion—Librations—Lunar topography—Physical condition. | |
| [X.—The sun] | [178] |
| Numerical data—Chemical nature—Temperature—Visible and invisible parts—Photosphere—Spots—Faculæ—Chromosphere—Prominences—Corona—The sun-spot period—The sun's rotation—Mechanical theory of the sun. | |
| [XI.—The planets] | [212] |
| Arrangement of the solar system—Bode's law—Physical condition of the planets—Jupiter—Saturn—Uranus and Neptune—Venus—Mercury—Mars—The asteroids. | |
| [XII.—Comets and meteors] | [251] |
| Motion, size, and mass of comets—Meteors—Their number and distribution—Meteor showers—Relation of comets and meteors—Periodic comets—Comet families and groups—Comet tails—Physical nature of comets—Collisions. | |
| [XIII.—The fixed stars] | [291] |
| Number of the stars—Brightness—Distance—Proper motion—Motion in line of sight—Double stars—Variable stars—New stars. | |
| [XIV.—Stars and nebulæ] | [330] |
| Stellar colors and spectra—Classes of stars—Clusters—Nebulæ—Their spectra and physical condition—The Milky Way—Construction of the heavens—Extent of the stellar system. | |
| [XV.—Growth and decay] | [358] |
| Logical bases and limitations—Development of the sun—The nebular hypothesis—Tidal friction—Roche's limit—Development of the moon—Development of stars and nebulæ—The future. | |
| [Appendix] | [383] |
| [Index] | [387] |