190 THE POPULAR SCIENCE MONTHLY. 



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 di- 

 rected 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 intensi- 

 fied 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 atmos- 

 phere 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 atmos- 

 phere. 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 at- 

 tribute 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 

 Yenus, 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 atmos- 

 pheres of Mars and the earth. Still this does not preclude the suppo- 

 sition 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 Sa- 

 hara. 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 con- 

 clude that Martial vegetation is of that color. 



