ELIAS LOOMIS, LL.D., PROFESSOR OF NATURAL PHILOSOPHY AND ASTRONOMY IN YALE COLLEGE; AUTHOR OF OF MATHEMATICS FOR SCHOOLS AND COLLEGES. NEW YORK: HARPER & BROTHERS, PUBLISHERS, 327 AND 335 PEARL STREET. THE NEW YORK PUBLIC LIBRARY 914555 TILDEN FOUNDATIONE R. Entered, according to Act of Congress, in the year 1865, by HARPER & BROTHERS, In the Clerk's Office of the Southern District of New York. PREFACE. THE design of the following treatise is to furnish a text-book for the instruction of college classes in the first principles of Astronomy. My aim has accordingly been to limit the book to such dimensions that it might be read entire without omissions, and to make such a selection of topics as should embrace every thing most important to the student. I have aimed to express every truth in concise and simple language; and when it was necessary to introduce mathematical discussions, I have limited myself to the elementary principles of the science. The entire book is divided into short articles, and each article is preceded by a caption, which is designed to suggest the subject of the article. Whenever it could be done to advantage, I have introduced simple mathematical problems, designed to test the student's familiarity with the preceding principles. At the close of the book will be found a collection of miscellaneous problems, many of them extremely simple, which are to be used according to the discretion of the teacher. I have dwelt more fully than is customary in astronomical text-books upon various physical phenomena, such as the constitution of the sun, the condition of the moon's surface, the phenomena of total eclipses of the sun, the laws of the tides, and the constitution of comets. I have also given a few of the results of recent researches respecting binary stars. It is hoped that the discussion of these topics will enhance the interest of the subject with a class of students who might be repelled by a treatise exclusively mathematical. My special acknowledgments are due to Professor H. A. Newton, who has read all the proofs of the work, and to whom I am indebted for numerous important suggestions. |