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Show 162 EXPLORATJON OF THE CANONS OF THE COLOJ~ADO. which head back in the plains and bad-lands, and cut across ridges and through mountains, are anaclinal, while those on the south side, which head near the summits of the mountains, and roll down to the foot of the range, and then turn off into the Green, are also cataclinal above, and monoclinal below. Taking the general course of Green River through the Uinta Mountains, without regard to the several portions, as abov/3 mentioned, it would be described as diaclinal. The explanation of the canons of Green River will assist us in understanding the origin of the lateral valleys and canons. The streams were there before the mountains were made-that is, the streams carved out the valleys, and left the mountains. The direction of the streams is indubitable evidence that the elevation of the· fold was so slow 3-S not to divert the streams, although the total amount of elevation was many thousands of feet. Had the fold been lifted more rapidly than the principal streams could have cut their channels, Green River would have been turned about it, and all the sma1ler streams and water-ways would have been cataclinal. Thw~ it is that the study of the structural chara.ctcristics of the valleys and canons teaches us, in no obscure way, the relation between the progress of upheaval and that of erosion and corrasion, showing that these latter were pari passu with the former, and that the agencies of nature produce great results-results no less than the carving of a mountain rango out of a much larger block lifted &om beneath the sea; not by an extravagant and violent use of power, but by the slow agencies which may be observed generaHy throughout the world, still acting in the same slow, patient manner. 1'here are yet some interesting facts to be observed concerning these inter-hog-back valleys. Their floors are usually lower than the general surface farther away from the mountains. There seem to be two causes for this. The great fold having been lifted and truncated prior to the exposure of the rocks farther away from the mountains, its strata present their edges, instead of their upper surfaces, to the down falling rain, and the softer beds are not so well shielded by the harder. Erosion hence progresses more rapidly than where the beds are approxim.ately horizontal. Again, the mountains, with peaks among the clouds, condense their Figure !;!.1.-llortle-Shoo Calion. |