[39] Struve wrote, in 1883:—“That changes do take place in the ring-system is sufficiently proved.” Trouvelot, Schiaparelli, and others have also remarked variations of a sufficiently decided character to be placed on record. [40] Herschel remarks that he saw this satellite in his 20-foot speculum two years before, viz. on Aug. 19, 1787, but he was then much engaged in observations of the satellites of Uranus. CHAPTER XIII. _URANUS AND NEPTUNE._ Discovery of Uranus.—Mistaken for a Comet.—True character revealed.—Period &c.—Observations.—Belts on Uranus.—Further Observations required.—The Satellites.—Discovery of Neptune.—The planet observed in 1795.—Period &c.—Observations.—Supposed Ring.—Satellite.—A trans-Neptunian Planet.—Planetary Conjunctions. _Discovery._—While Sir W. Herschel was a musician at Bath he formed the design of making a telescopic survey of the heavens. When engaged in this he accidentally effected a discovery of great importance, for on the night of March 13, 1781, an object entered the field of his 6·3-inch reflector which ultimately proved to be a new major planet of our system. The acute eye of Herschel, directly it alighted upon the strange body, recognized it as one of unusual character, for it had a perceptible disk, and could be neither fixed star nor nebula. He afterwards found the object to be in motion, and its appearance being “hazy and ill-defined” with very high powers he was led to regard it as a comet, and communicated his discovery to the Royal Society at its meeting on April 26, 1781. His paper begins as follows:— “On Tuesday, March 13, 1781, between 10 and 11 in the evening, while I was examining the small stars in the neighbourhood of H Geminorum, I perceived one that appeared visibly larger than the rest. Being struck with its uncommon magnitude, I compared it to H Geminorum and the small star in the quartile between Auriga and Gemini, and finding it so much larger than either of them suspected it to be a comet.... The power I had on when I first saw the comet was 227.” The supposed “comet” soon came under the observation of others, including Maskelyne the Astronomer Royal, and Messier, the “Comet Ferret” of Paris. The latter, in a letter to Herschel, said:—“Nothing was more difficult than to catch it, and I cannot conceive how you could have hit this star or comet several times, for it was absolutely necessary for me to observe it for several days in succession before I could perceive that it was in motion.”