To mention some of these. The nearest star to the earth, so far as we yet know, is Alpha Centauri, which is distant from us about 25 billions of miles. The light from this star, travelling at the stupendous rate of about 186,000 miles per second, takes about 4-1/4 years to reach our earth, or, to speak astronomically, Alpha Centauri is about 4-1/4 "light years" distant from us. Sirius--the brightest star in the whole sky--is at twice this distance, _i.e._ about 8-1/2 light years. Vega is about 30 light years distant from us, Capella about 32, and Arcturus about 100. The displacements, consequent on the earth's movement, have, however, plainly nothing to say to any real movements on the part of the stars themselves. The old idea was that the stars were absolutely fixed; hence arose the term "fixed stars"--a term which, though inaccurate, has not yet been entirely banished from the astronomical vocabulary. But careful observations extending over a number of years have shown slight changes of position among these bodies; and such alterations cannot be ascribed to the revolution of the earth in its orbit, for they appear to take place in every direction. These evidences of movement are known as "proper motions," that is to say, actual motions in space proper to the stars themselves. Stars which are comparatively near to us show, as a rule, greater proper motions than those which are farther off. It must not, however, be concluded that these proper motions are of any very noticeable amounts. They are, as a matter of fact, merely upon the same apparently minute scale as other changes in the heavens; and would largely remain unnoticed were it not for the great precision of modern astronomical instruments. One of the swiftest moving of the stars is a star of the sixth magnitude in the constellation of the Great Bear; which is known as "1830 Groombridge," because this was the number assigned to it in a catalogue of stars made by an astronomer of that name. It is popularly known as the "Runaway Star," a name given to it by Professor Newcomb. Its speed is estimated to be at least 138 miles per second. It may be actually moving at a much greater rate, for it is possible that we see its path somewhat foreshortened. A still greater proper motion--the greatest, in fact, known--is that of an eighth magnitude star in the southern hemisphere, in the constellation of Pictor. Nothing, indeed, better shows the enormous distance of the stars from us, and the consequent inability of even such rapid movements to alter the appearance of the sky during the course of ages, than the fact that it would take more than two centuries for the star in question to change its position in the sky by a space equal to the apparent diameter of the moon; a statement which is equivalent to saying that, were it possible to see this star with the naked eye, which it is not, at least twenty-five years would have to elapse before one would notice that it had changed its place at all!