The great impetus given to the study of astronomy by Galileo, in 1609, was followed up by Huygens in 1655 with his improvement, by Gregory’s reflecting telescope of 1663, and Newton’s in 1668. In 1733 Chester More Hall invented the achromatic object glass of crown and flint glass. In 1758 John Dolland reinvented and introduced the same in the manufacture of telescopes. In 1779 Herschel built his reflecting telescope, and in March, 1781, he discovered the planet Uranus. In 1789 he built his great reflector. It was while the latter telescope was exploring the heavens that the Nineteenth Century began, and in the early part of this century Herschel laid before the Royal Society a catalogue of many thousand nebulæ and clusters of stars. Among the great telescopes of the Nineteenth Century may be mentioned that made in London in 1802 for the observatory of Madrid, which cost £11,000; the great reflecting telescope of the Earl of Rosse, erected at Parsonstown, in Ireland, in 1842-45. This was 6 feet diameter, 54 feet focal length, and cost over £20,000; the magnificent equatorial telescopes set up at the National Observatories at Greenwich and Paris in 1860; Foucault’s reflecting telescope at Paris, 1862, whose mirror was 31½ inches diameter, and focal length 17¾ feet; Mr. R. S. Newall’s telescope, set up at Gateshead by Cookes, of York, in 1870; object glass, 25 inches, tube, 30 feet; Mr. A. Ainslie Common’s reflecting telescope, Ealing, Middlesex, 1879, mirror, 37½ inches diameter, tube, 20 feet; the telescope at the United States Observatory, at Washington, 1873, object glass, 26 inches, tube, 33 feet long; and the large refracting telescope by Howard Grubb, at Dublin, for Vienna, 1881. [Illustration: FIG. 194.--TELESCOPE AT LICK OBSERVATORY.] In more recent times the great refracting telescope by Alvan Clark & Sons, for the Lick Observatory on Mount Hamilton, California, in 1888, attracted attention as superior to anything in existence up to that time. This is shown in Fig. 194. The supporting column and base are of iron, weighing twenty-five tons. This rests on a masonry foundation, which forms the tomb of James Lick, its founder. The tube is 52 feet long, 4 feet diameter in the middle, tapering to a little over 3 feet at the ends. The object glass is 36 inches in diameter, and weighs, with its cell, 530 lbs. The steel dome is 75 feet 4 inches in diameter, and the weight of its moving parts is 100 tons. This instrument was perfectly equipped with all gauges, scales, photographic and spectroscope accessories, and fulfilled the condition imposed in the trust deed of James Lick, of being “superior to and more powerful than any telescope made.” It is a giant among instruments of precision, and its ponderous aspect still asserts the dignity of its purpose, and impresses even the frivolous visitor with a silent and thoughtful respect.