Page:Popular Science Monthly Volume 23.djvu/653

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light as from a desert absolute. Far as you can look or listen there comes not the faintest sign or whisper of living thing. No bird visits those forgotten hills, no insect stirs about your feet or beats with humming wings the air; the very wind is silent, and from the glowing buttes, as from a furnace, the heated atmosphere rises in shimmering columns. It seems as if it had never rained, or, if it has rained, it seems as though it would never rain again. Here is the trail by which, in 1863, passed General Sully and his train when all these hill-tops were alive with hostile Sioux. The Indians are long since gone, but the trail remains unchanged, and can be easily followed after a lapse of twenty years. Yonder, along that other trail still so clearly visible over the distant buttes, went Custer and his band when they marched away to the west and disappeared from human sight forever. The climate is an arid one, and the process of erosion slow. Looking out over the landscape as we now see it, none would imagine that all this territory was at one time favored with a climate perhaps nearly semi-tropical, that over all this wide area were waving forests of perpetual green, stretching away to the north, south, east, and west, almost to the limits of the so-called "Plains." Yet such is the case, and this complete transition from the wealth of primeval woods to the poverty of semi-desert has been brought about not by the devastation of short-sighted man, but by the orderly procedure of all those indefinite forces which for convenient description men sum up as Nature. The evidence of this transition is not far to seek. Scattered over the grassy low-lands, crowning many an isolated pillar of sandstone or clay, lying here and there on all the high hills, are remnants of gigantic trees, remnants more or less perfectly silicified, stumps, boles, and branches. In some localities these "petrified stumps" cover the whole face of

PSM V23 D653 Sectional views of silicified wood fibre.jpg
Fig. 1.—Longitudinal Section of Silicified Wood, x 150. Fig. 2.—Microscopic Section of the Wood of the Common Larch, cut in the Long Direction of the Fibers.

the country, and scores have been carried away on flat-cars to decorate the lawns of those able to pay freight on such unwieldy "curiosities." Scientists are frequently disposed to doubt petrifactions, and are often compelled to disappoint popular expectation in regard to forms most