Uranus is attended by several satellites. It was once thought that there were eight, of which six were due to Sir W. Herschel, the other two being of modern discovery. Astronomers are, however, now agreed that no more than four satellites can justly be recognised as known to exist, and they are so minute in size that only the very largest telescopes will show them; and therefore our knowledge of them is extremely limited. Sir W. Herschel’s idea that he had seen six satellites appears to have resulted from his having on some occasions mistaken some very small stars for satellites. Two only of his six are thought to have been real satellites. The other two recognised satellites were found both in 1847, one by Lassell, and the other by O. Struve. Uranus revolves round the Sun in rather more than 84 years, at a mean distance of 1781 millions of miles. Its apparent diameter, seen from the Earth, does not vary much from 3½″ which corresponds to about 31,000 miles. It has been calculated that the light received from the Sun by Uranus would be about the amount furnished by 300 full Moons seen by us on the Earth, though another authority increases this to 1670 full Moons. From Uranus Saturn can be seen, and perhaps Jupiter, both as inferior planets, just as we see Venus and Mercury; but all the other inner planets, including Mars and the Earth, would be hopelessly lost to view, because perpetually too close to the Sun. Possibly, however, they might, on rare occasions, be seen in transit across the Sun’s disc. Neptune, of course, would be visible and be the only superior planet. The Sun itself would appear to an observer on Uranus as a very bright star, with a disc of 1¾′ of arc in diameter. CHAPTER XII. NEPTUNE.