A main difference between the two kinds of telescope thus resides in the fact that the star-rays--or any other kind of light-rays--when first captured, pass, in one case, _through_ the glass on which they fall, and, in the other case, are thrown off _from_ the mirror. In both cases, the whole amount of light so captured is gathered into a small compass, so as to be available for human sight. [Illustration: EYE-PIECE OF THE LICK TELESCOPE.] Once more, let me remind you, it should be always kept clearly in mind that every object that is seen by us--from a mote of dust to a sun, from a coal-scuttle to a star--is perceived purely and solely by the light which it gives out, either intrinsic or reflected light. Countless myriads of rays pass from the surface of the thing seen to our eyes, picturing there, on the sensitive retina, a fleeting vision of its form. All the leading Governments in Europe have observatories for the study of the heavens, which are furnished with the best instruments of modern construction. The principal observatories are those at Paris, Berlin, Vienna, Nice; Dorpat, the seat of a celebrated university founded by Gustavus Adolphus, of Sweden, in 1630; Pulkowa, near St. Petersburg; Lisbon, and at Greenwich in England. In America, though only in recent years has astronomy been cultivated with ardor, there are observatories of more or less importance,--the National Observatory at Washington, D. C.; the Cincinnati Observatory, projected by the late General O. M. Mitchel; the Dudley Observatory, founded by Mrs. Blandina Dudley in honor of her husband, at Albany, N. Y.; the Lick Observatory, founded by James Lick, on Mount Hamilton, Cal.; and the Yerkes Observatory, connected with the Chicago University, founded by Charles T. Yerkes. Besides these, there are observatories connected with some of our other leading universities and colleges, as those of Harvard, at Cambridge, Mass.; Yale University; Williams College; West Point Military Academy; Amherst College; Princeton; Dartmouth; Michigan University; Hamilton College, N. Y., and several others. [Illustration: LICK OBSERVATORY IN WINTER, FROM THE EAST.] The largest and best refracting telescopes in the world are those at Lick Observatory and at Yerkes Observatory, now in charge of Professor E. E. Barnard, who, while at the head of the Lick Observatory, discovered the fifth satellite of Jupiter, and determined the character of the inner ring of Saturn. The best reflecting telescope is that of Lord Rosse, at Birr Castle, in Kings County, Ireland. [Illustration: E. E. BARNARD.]