We pass by the belt of asteroids, and over a distance many times greater than that which separates the earth from the sun, till we approach our own world. Here, close beside it as it were, in comparison with the enormous spaces which intervene between it and Saturn and Jupiter, we find a planet whose size and features are in striking contrast to those of the great globe we have just quitted. It is Mars, which shines so red and looks so large in the sky because it is so near, but whose diameter is only about half that of our earth. This is indeed properly to be called a neighbor world, but the planetary spaces are so immense that this neighbor is at closest still about thirty-four million miles away. [Illustration: FIG 63.--THREE VIEWS OF MARS.] [Illustration: FIG 64.--MAP OF MARS.] Looking across that great gulf, we see in our engraving (Fig. 63)--where we have three successive views taken at intervals of a few hours--a globe not marked by the belts of Jupiter or Saturn, but with outlines as of continents and islands, which pass in turn before our eyes as it revolves in a little over twenty-four and a half of our hours, while at either pole is a white spot. Sir William Herschel was the first to notice that this spot increased in size when it was turned away from the sun, and diminished when the solar heat fell on it; so that we have what is almost proof that here is ice (and consequently water) on another world. Then, as we study more, we discern forms which move from day to day on the globe apart from its rotation, and we recognize in them clouds sweeping over the surface,--not a surface of still other clouds below, but of what we have good reason to believe to be land and water. By the industry of numerous astronomers, seizing every favorable opportunity when Mars comes near, so many of these features have been gathered that we have been enabled to make fairly complete maps of the planet, one of which by Mr. Green is here given (Fig. 64). Here we see the surface more diversified than that of our earth, while the oceans are long, narrow, canal-like seas, which everywhere invade the land, so that on Mars one could travel almost everywhere by water. These canals seem also in some cases to exist in pairs or to be remarkably duplicated. The spectroscope indicates water-vapor in the Martial atmosphere, and some of the continents, like “Lockyer Land,” are sometimes seen white, as though covered with ice: while one island (marked on our map as Hall Island) has been seen so frequently thus, that it is very probable that here some mountain or tableland rises into the region of perpetual snow.