TWENTIETH CENTURY TEXT-BOOKS
EDITED BY
A. F. NIGHTINGALE, Ph.D., LL.D.
FORMERLY SUPERINTENDENT OF HIGH SCHOOLS, CHICAGO
TWENTIETH CENTURY TEXT-BOOKS
A TEXT-BOOK OFASTRONOMY
BY
GEORGE C. COMSTOCK
DIRECTOR OF THE WASHBURN OBSERVATORY AND
PROFESSOR OF ASTRONOMY IN THE
UNIVERSITY OF WISCONSIN
NEW YORK
D. APPLETON AND COMPANY
1903
Copyright, 1901
By D. APPLETON AND COMPANY
[Pg v]
PREFACE
The present work is not a compendium of astronomyor an outline course of popular reading in that science. Ithas been prepared as a text-book, and the author has purposelyomitted from it much matter interesting as well asimportant to a complete view of the science, and has endeavoredto concentrate attention upon those parts of thesubject that possess special educational value. From thispoint of view matter which permits of experimental treatmentwith simple apparatus is of peculiar value and isgiven a prominence in the text beyond its just due in awell-balanced exposition of the elements of astronomy,while topics, such as the results of spectrum analysis,which depend upon elaborate apparatus, are in the experimentalpart of the work accorded much less space thantheir intrinsic importance would justify.
Teacher and student are alike urged to magnify theobservational side of the subject and to strive to obtain intheir work the maximum degree of precision of which theirapparatus is capable. The instruments required are fewand easily obtained. With exception of a watch and a protractor,all of the apparatus needed may be built by anyone of fair mechanical talent who will follow the illustrationsand descriptions of the text. In order that properopportunity for observations may be had, the study shouldbe pursued during the milder portion of the year, betweenApril and November in northern latitudes, using clear[Pg vi]weather for a direct study of the sky and cloudy days forbook work.
The illustrations contained in the present work areworthy of as careful study as is the text, and many ofthem are intended as an aid to experimental work andaccurate measurement, e. g., the star maps, the diagramsof the planetary orbits, pictures of the moon, sun, etc. Ifthe school possesses a projection lantern, a set of astronomicalslides to be used in connection with it may bemade of great advantage, if the pictures are studied as anauxiliary to Nature. Mere display and scenic effect are oflittle value.
A brief bibliography of popular literature upon astronomymay be found at the end of this boo