Mars, one of the planets in the solar system, has its orbit outside that of the Earth, and is therefore one of the so-called superior planets. At its nearest position Mars is 48,000,000 miles from the Earth, no other planet except Venus approaching us more nearly. Its diameter is about 5,000 miles; so its surface is only two-fifths as extensive as the Earth's. Its density is much less - about three-quarters that of the Earth; so a pound weight placed on its surface would not weigh much more than six ounces, and a ponderous elephant would, if there, be able to jump about with the agility of a fawn. Mars travels in an orbit whose centre is 130,000,000 miles away from the sun; when nearest to the sun, it is 12li,000,000 miles away. When farthest from it, the distance is 152,000,000 miles, the average distance being about 139,000,000 miles. The heat and light which Mars receives from the sun, therefore, vary enormously, and so cause a difference in the lengths of winter and summer in his N. and S. hemispheres, the seasons in the N. hemisphere being far more temperate than those in the S. The Martial year is about 687 of oar days, and its day 40 minutes longer than ours. Viewed with the telescope, large dark green spots are seen, the rest of the surface being of a ruddy tint, except at the two poles, where two white spots are observed and considered to be due to large masses of snow and ice. It has been supposed that the greenish spots are oceans, and the ruddy parts land. The spectroscope has shown that watery vapour is present in Mars' atmosphere, and appearances like huge rain-clouds sometimes obscure a part of the planet for a considerable period. Physical processes seem to go on there much the same as on our planet; hence many believe that Mars is inhabited and forms, in fact, a miniature picture of the Earth.