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Show RECONNAISSANCE IN THE UTE COUNTRY. 75 porphyry and trachyte. We continued our march along the margin of the San Luis Park, and connected with the line of our outward march at Del Norte. Geological observations on Ute reconnaissance from FiscWs Ranch to Pueblo via ( Jochetopa Pass, head of Gunnison's River y and Lake Greek Pass. As the several lines of observations have nearly encircled a part of the San Luis Valley, it may not be irrelevant to enter here a more detailed description of this portion of that extensive inclosure. That part of the valley north of a due west line from Fort Garland is a treeless plain, descending toward the south side, with the Rio Grande on the west. That portion under consideration includes an area of about 700 square miles, with a mean elevation of 8,500 feet. The central portion receives the drainage of the mountain- ranges on the north and northeast into a lake without an outlet. The extent of the waters of this lake varies with the season, increases with the melting of the snows, and equilibrium is maintained by evaporation. In the vicinity of the lake, and so far as its waters impart moisture to the low and changing margin, vegetation is fresh and exuberant, resembling an oasis in a desert. The lake, with these conditions, comprises about one tenth of the area under review. The remaining portion is arid, the surface more often monopolized by artemisia and cacti. As a cattle- range it is not to be recommended. True, herds are fed the year round on the scanty bunch- grass as nature provides and cures it, but my observations tend to the conclusion that there can be no practical development in cattle reared under such circumstances. Sheep, however, thrive, are healthy, increase rapidly, and are comparatively free from disease. The valley, or approach to the Cochetopa Pass from the Atlantic side, is principally red porphyry. At Camp No. 7, elevated 8,100 feet, is a fragment of a ledge of conglomerate which 1 traced 360 feet upon the mountain- slope; still 50 feet above the latter point is a formation ( in situ) of soft, gray mottled limestone resting on a hard brown limestone. These formations are 50 feet thick, in horizontal strata, resting against porphyry. The rocks farther up on the slope are of a brown trachyte, and the face of the ledge is much water- worn. The lines are fresh, as if the water had but recently receded. Soon after leaving Camp 7, the surface- deposits conceal the more solid formations. After descending the Pacific slope about 400 feet, fragments of white limestone were observed, and lower down in the valley, in regular strata, at intervals, as low as our encampment. Mr. Prout notes " that between Camps 8 and 9 the route lies over a mesa of sandstone underlaid by granite, which crops out here and there. There is very little soil, consisting mainly of decomposed granite and sandstone. Near Camp 9 the Tumitchi flows, in a canon 100 to 300 feet deep; much rock exposed- dark gray sandstone.(?) About two miles above this point the canon is deeper, with walls of red feldspathic granite." The foot- hills, down to near the junction of Pass Creek and Tumitchi Creek, are of gray shale and white calcareous slate, similar to the gray mottled limestone mentioned between Camps 6 and 7. At the junction of the creeks named is a prominent point of coarse |