Uranus was discovered by Herschel in 1781 (March 13), and is the next planet beyond Saturn, being 1,783 million miles from the sun. His diameter is over 30,000 miles, and his volume is about ninety times that of the Earth. His density is about 15/100 that of the Earth, rather less than that of water, so that his mass is about fifteen times as much as that of the Earth, an amount which makes him more than outweigh Mercury, Venus, the Earth, and Mars combined. All astronomers do not agree in their estimation of these numbers, Uranus us being too far away for measurements to be more than approximate. Gravity on his surface is only three-quarters of what it is here, so that a ponderous beast here could move about with springful alacrity if transported through space to that far-off planet. Uranus, being so far from the sun, naturally loses the benefit of his light and heat; in fact, to an inhabitant of Uranus -- if there be one -- the sun would merely appear as a bright star does to us. A great pecularity exists in the arrangement of his satellites. Unlike those of other planets, they do not move approximately in the plane in which the planet travels, but circle him in a plane nearly at right angles to his orbit (about 76°).