Across the Zodiac, page 209 by Percy Greg
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every kind, each species occupying the level best suited to it, from the reed-supported orange-like alva of the lowlands to the tall astyra, above which stretched the timber forests extending as high as trees could grow, while between these and the permanent snow-line lay the yellowish herbage of extensive pastures. A similar mountain range on earth would have presented a greater variety of colouring and scenery, the total absence of glaciers, even in the highest valleys, creating a notable difference. The truth is that the snows of Mars are nowhere deep, and melt in the summer to such an extent that that constant increase whose downward tendency feeds Terrestrial glaciers cannot take place. Probably the thin atmosphere above the snow-line can hold but little watery vapour. Esmo was of opinion that the snow on the highest steeps, even on a level plateau, was never more than two feet in depth; and in more than one case a wind-swept peak or pinnacle was kept almost clear, and presented in its grey, green, or vermilion rocks a striking contrast to the masses of creamy white around it. This may explain the very rapid diminution of the polar ice-caps in the summer of either, but especially of the Southern hemisphere; and also the occasional appearance of large dark spots in their midst, where the shallow snow has probably been swept away by the rare storms of this planet from an extensive land surface. It is supposed that no inconsiderable part of the ice and snow immediately surrounding the poles covers land; but, though balloon parties have of late occasionally reached the poles, they have never ventured to remain there long enough to disembark and ascertain the fact.
Towards evening the stream turned more decidedly to the north, and at this point Esmo brought out an instrument constructed somewhat on the principle of a sextant or quadrant, but without the mirror, by which we were enabled to take reliable measures of the angles. By a process which at that time I did not accurately follow, a