Page:Popular Science Monthly Volume 4.djvu/202

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that more than one of them can be seen at a time. The seas and the straits which connect them constitute a very distinctive character of Mars, and they are generally perceived whenever the telescope is directed upon that planet.

The continents of Mars are tinged of an ochre-red color, and its seas have for us the appearance of blotches of grayish green intensified by the contrast with the color of the continents. The color of the water on Mars is therefore that of terrestrial water. But why is the land there red? It was at one time supposed that this tinge must be owing to the Martial atmosphere. It does not follow that, because our atmosphere is blue, the atmosphere of the other planets must have the same color. Hence it was permissible to suppose that the atmosphere of Mars was red. In that case the poets of that world would sing the praises of that ardent hue, instead of the tender blue of our skies. In place of diamonds blazing in an azure vault, the stars would be for them golden fires flaming in a field of scarlet; the white clouds suspended in this red sky, and the splendors of sunset, would produce effects not less admirable than those which we behold from our own globe.

But the case is otherwise. The coloration of Mars is not owing to its atmosphere; for, although the latter is spread out over the entire planet, neither its seas nor its polar snows assume the red tinge; and Arago, by showing that the rim of the planet's disk is of a less deep tinge than the centre, proved that the color is not due to the atmosphere. If it were, then the rays reflected from the margin to us would be of a deeper red than those reflected from the centre, as having to pass through a greater height of atmosphere. May we attribute to the color of the herbage and plants, which no doubt clothe the plains of Mars, the characteristic hue of that planet, which is noticeable by the naked eye, and which led the ancients to personify it as a warrior? Are the meadows, the forests, and the fields, on Mars, all red? An observer, looking out from the moon, or from Venus, upon our own planet, would see our continents deeply tinged with green. But, in the fall, he would find this tint disappearing at the latitudes where the trees lose their leaves. He would see the fields varying in their hues, and then would come winter, when they would be covered with snow for months. On Mars the red coloration is constant; it is observed at all latitudes, and in winter no less than in summer. It varies only in proportion to the clearness of the atmospheres of Mars and the earth. Still this does not preclude the supposition that the Martial vegetation has its share in producing the red hue of the planet, though it be principally due to the color of the soil. The land cannot be all over bare of vegetation, like the sands of Sahara. It is very probably covered with a vegetation of some kind, and, as the only color we perceive on Mars's terra firma is red, we conclude that Martial vegetation is of that color.