Originally published in 1893. PREFACE: The object of the following pages is not to propound any new hypothesis, but simply to explain and discuss theories which have been supported by well known astronomers and other men of science. Hypotheses which are merely paradoxes will of course not be considered. The latest results respecting the distribution of stars and nebulae, their relative motions, and the physical constitution of the heavenly bodies, will be given; and it is hoped that the work will prove of interest to the general reader as well as to the student of astronomy. Illustrated throughout, this works is thoroughly recommended for inclusion on the bookshelf of any one interested in the universe. Many of the earliest books, particularly those dating back to the 1900's and before, are now extremely scarce and increasingly expensive. We are republishing these classic works in affordable, high quality, modern editions, using the original text and artwork.