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Show 82 KECONNAISSANCE IN THE UTE COUNTRY. reviewing, but that portion of your instructions relating to incidentals were recorded mainly in specific facts; a further illustration of their correlations may not be irrelevant. On the 8th of May we started from Pueblo, and before the close of the day came upon limestone of the Cretaceous age. On the three succeeding days, I traced their contiguous formations to near the mouth of the Huerfano Canon, and classified them into a section. I traced the equivalents of these formations from the mouth of the caiion at Canon City, down the Arkansas River to Pueblo. Here we have over one hundred miles of very interesting rocks as familiar to me as my own door- yard; having traced them for many miles in Kansas, on a survey of that State. After crossing the Eastern Range, we came into the San Luis Valley. On the very margin, I observed indications that this broad and extensive valley had once been a lake. Along the several lines these indications multiplied into relative facts. Above Wagon- Wheel Gap we entered a broad valley in which I reported the existence of yellow clay and clay slate of considerable thickness. Next day these were noted in formidable thickness lying against the slope of the mountain. Above Antelope Caiion are remnants of clay and conglomerate formations reaching nearly up to timber- line, and once filling this portion of the valley. At lower levels the walls shows the mark of fiuviatile action as plainly as if the waters had just receded. These and like phenomena exist hi nearly every valley, pointing to forces and conditions that have long since ceased. The volcanic action may be remarked upon as follows: At the exit of the Rio Grande from the mountains, basalt intrusions from below occur, at Camp Loma, volcanic flux from above. Each volcanic center has left its own peculiar deposits; these may readily be distinguished one from another. The frequent change in these elements along our lines, leads me to the opinion that the centers were numerous and limited in extent. Except, perhaps, in one instance, on the Ute trail over the Central Range, the slope of the Saguache Valley has been deluged with volcanic flux from near the summit to the base; that, too, comparatively recently, since the valley was formed. This volcanic matter I traced to the Cochetopa Valley, where I found it under peculiar circumstances alike novel and'instructive, if I should give scope to my imagination. I might locate the center between Cochetopa and Clear Creek Passes. In a comparative view of the structural relations of the different mountain ranges, the igneous productions are far more predominant than the granitic classes. This remark will apply more particularly to the Pacific slope, where but in one instance a large scope of granite was observed. We crossed this granite field in five miles- on the high grounds west of Lake Fork, ten miles above Gunnison River, and again on a parallel line in Tumitchi Valley, where it is exposed in ledges of 150 feet. Admitting that the formations of the two valleys coalesce, or are contiguous, it would only make an insignificant area of about 75 square miles. But immediately after crossing Lake Creek Pass, and attaining the Atlantic slope and the waters of the Arkansas River, granite is the prevailing rock. On the Pacific slope, too, I found more definite indications among tbe older rocks of the reconstruction of their disintegrated matters into more definite forms. In the valley of Tumichi Creek occurs a stratified quartzose forma tion of 500 feet in thickness, granular at the base, and gradually shad- |