The lower slopes of the hills were covered
with orchards of 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.
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