also contain accounts of the curious, and as yet unexplained, phenomena attending their appearances on the disc of the planet.
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 con-
