Although Herschel made several important observations on the Moon, and measured the heights of the lunar mountains, he was not a devoted student of our satellite. Caroline Herschel remarks in her memoirs that if it had not been for clouds or moonlight, neither her brother nor herself would have got any sleep; adding that Herschel on the moonlight nights prepared his papers or made visits to London. However, he did make some investigations, and in 1783 and 1787 believed himself to have witnessed the eruption of three lunar volcanoes. He afterwards concluded, however, that what he believed to be eruptions was really the reflexion of earth-shine from the white peaks of the lunar mountains. Herschel never discovered a comet, leaving that branch of astronomy to his sister, who discovered eight of these objects. He was, however, much interested in comets, and attentively studied them, introducing the terms of “head,” “nucleus,” and “coma.” Herschel anticipated the view that comets are not lasting, but are partly disintegrated at their perihelion passages. He was of opinion that they travelled from star to star. The extent of their tails and appendages he thought to be a test of their age. We have now completed our sketch of Herschel’s important labours regarding our Solar System. As Miss Clerke says, “A whole cycle of discoveries and successful investigations began and ended with him.” But through observing the stars he made a further discovery in connection with the Solar System; indeed, one of the greatest discoveries in the history of astronomy—the movement through space of the Sun, carrying with it planets and comets.