theory—Faye’s hypothesis—Ball’s exposition—The meteoritic theory of Proctor—Its extension by Lockyer—Evolution of the stars—Vogel’s order of evolution—Tidal friction: work of Darwin—See’s explanation of double stars—Future of the Universe A CENTURY’S PROGRESS IN ASTRONOMY. CHAPTER I. HERSCHEL THE PIONEER. In astronomy, as in other sciences, the past hundred years has been a period of unparalleled progress. New methods have been devised, fresh discoveries have been made, new theories have been propounded; the field of work has widened enormously. In fact, the science of the heavens has become not only boundless in its possibilities, but more awe-inspiring and marvellous. To whom in the main is this great advance due? To the great pioneer of what may be called modern astronomy—William Herschel. Not only did Herschel reconstruct the science and widen its bounds, but his powerful genius directed the course of nineteenth century research. As an astronomical observer he has never been surpassed. In the breadth of his views he was equalled only by Newton; and indeed he excelled Newton in his unwearied observations and his sweeping conceptions of the Universe. To quote his own remark to the poet Campbell, he “looked farther into space than ever human being did before him.” Herschel studied astronomy in all its aspects. In all the branches of modern astronomy he was a pioneer. He observed the Sun, Moon, and planets, devoting special attention to Mars and Saturn. He doubled the diameter of the Solar System by the discovery of Uranus. He discovered several satellites and studied comets. He was pre-eminently the founder of sidereal astronomy. He discovered binary stars, thus tracing the law of gravitation in the distant star-depths; while to him is due the credit of the discovery of the motion of the Solar System. He founded the study of star-clusters and nebulæ, propounded the nebular hypothesis, and devised two methods of star-gauging. Above all, he was the first to attempt the solution of one of the noblest problems ever attacked by man—the structure of the Universe. In fact, the latter problem was the end and aim of his observations. As Miss Clerke remarks, “The magnificence of the idea, which was rooted in his mind from the start, places him apart from and above all preceding observers.” Most of the departments of modern astronomy find a meeting-place in Herschel, as the branches run to the root of the tree. He discussed astronomy from every point of view. Before, however, proceeding to examine the work of this great man, it is well to note a few of his characteristics. These characteristics, once understood, give us the key to his researches. Before we can master Herschel the astronomer we must understand Herschel the man.