HERSCHEL discovered in January, 1787, the two brighter satellites of _Uranus_, now called _Oberon_ and _Titania_. They are among the faintest objects in the solar system. A later discussion of all his observations led him to the belief that there were four more, and he gives his observations and computations in full. He says that of the existence of additional satellites he has no doubt. Of these four, three were exterior to the most distant satellite _Oberon_, the other was "interior" to _Titania_.
It was not until 1834 that even _Oberon_ and _Titania_ were again observed (by Sir JOHN HERSCHEL) with a telescope of twenty feet, similar to that which had discovered them, and not until 1847 was the true state of this system known, when Mr. LASSELL discovered _Ariel_ and _Umbriel_, two satellites interior to _Titania_, neither of which was HERSCHEL'S "interior" satellite. In 1848 and later years Mr. LASSELL, by the aid of telescopes constructed by himself, fully settled the fact that only four satellites of this planet existed. In 1874 I examined the observations of HERSCHEL on his supposed "interior" satellite, thinking that it might be possible that among the very few glimpses of it which he recorded, some might have belonged to _Ariel_ and some to _Umbriel_, and that by combining rare and almost accidental observations of two satellites which really existed, he had come to announce the existence of an "interior" satellite which had no existence in fact. Such I believe to be the case. In 1801, April 17, HERSCHEL describes an interior satellite in the position angle 189°, distant 18" from the planet. At that instant _Umbriel_, one of Mr. LASSELL'S satellites, was in the position 191°, and distant 21" from _Uranus_, in the most favorable position for seeing it. The observation of 1794, March 27, _may_ belong to _Ariel_. At the best the investigation is of passing interest only, and has nothing to do with the question of the discovery of the satellites. HERSCHEL discovered the two brighter ones, and it was only sixty years later that they were properly re-observed by Mr. LASSELL, who has the great honor of having added as many more, and who first settled the vexed question of satellites _exterior_ to _Oberon_, and this with a reflecting telescope made by himself, which is unequalled by any other of its dimensions.
