One result of Herschel’s discoveries among the stars and nebulæ is that his studies of the Sun and planets, with the exception of the discovery of Uranus, have been completely thrown into the shade. Nevertheless, his work in solar and planetary astronomy alone would have gained for him a higher position in astronomy than his contemporaries. The planets, satellites, and comets were all attentively studied by the great astronomer; indeed, the scientific investigation of the surfaces of Mars and Saturn began with Herschel. “His attention to the Sun,” Miss Clerke truly remarks, “might have been exclusive, so diligent was his scrutiny of its shining surface.” Sunspots were specially investigated by Herschel, who closely studied their peculiarities, regarding them as depressions in the solar atmosphere. He also paid much attention to the faculæ, but could not observe them to the north and south of the Sun, thus proving their connection with the spots which are confined to the regions north and south of the equator. “There is all over the Sun a great unevenness,” said Herschel, “which has the appearance of a mixture of small points of an unequal light; but they are evidently a roughness of high and low parts.” Herschel’s solar observations were very valuable, and did much for our knowledge of the orb of day. His theory of the Sun’s constitution—a development of the hypothesis put forward by _Alexander Wilson_ (1714-1786), Professor of Astronomy in Glasgow—was, however, very far from the truth. This was almost the only instance in which Herschel was mistaken. He regarded the Sun as a cool, dark globe, “a very eminent, large, and lucid planet, evidently the first, or, in strictness of speaking, the only primary one of our system.” In his opinion an extensive atmosphere surrounded the Sun, the upper stratum forming what Schröter named the “photosphere.” This atmosphere, estimated as two or three thousand miles in depth, was regarded as giving out light and heat. Below this shining atmosphere there existed, Herschel believed, a region of clouds protecting the globe of the Sun from the glowing atmosphere, and reflecting much of the light intercepted by them. The spots were believed to be openings in these atmospheres, caused by the action of winds, the umbra or dark portion of the spot thus representing the globe of the Sun, which Herschel believed to be “richly stored with inhabitants.” This theory held its ground for many years. Newton, it is true, believed the Sun to be gaseous, but he propounded no hypothesis of its constitution. Herschel’s theory, on the other hand, was fully developed, plausible, and attractive. It was held by eminent men of science until 1860, when the revelations of the spectroscope showed it to be quite untenable. The theory was supported for many years by Sir John Herschel, who, however, abandoned it in 1864. Herschel made several attempts to ascertain whether any connection existed between the state