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Show APPENDIX NN. 1295 in the Truckee Caflon, as well as white thorn and manz? nita. Six miles from the entrance of tho cation, Squaw Valley is reached. Squaw Creek flows through this valley, >* Inch has a broad fertile floud- plalu. At the head of the valley there is a steep preci-j » ' ce wipi rounded bases. The rock is porphyritic diorite. The southern side of Squaw Valley is steeper than the northern. A little farther down the Truckee Cofion is Clara-ville/ the s. te of an abandoned mining town. Several prospect- holes are seen in the north wall of the cafion. In 1863 a population of 500 people gathered at this point amid gieat excitement. Soon afterward the mines gave out, and it is difficult uow to find the slightest vestiges of a former settlement. The gold occurred in placer- diggings. Beyond Claraviile the rivor nakes a northerly eonrsu, and the ease side of the caflon is blue basalt as far as Truckee. Tors of trachyte 30 feet high outcrop along the western side. Near the fish ranch there is a very irregularly formed butto of gray baenlt Laving a laminated structure. Tbe laminrc are about half an inch thick. The rock < n both sides of the canon has undergone much disintegration. At the town of Truckee coarse- grained gray granite outcrops. It is similar to the tock fornm g the greater part of the western summit. The rblge norrh of Truckee Calion is the northernmost on tho western side of Lake Tahoe. Tho riilge extends as far as a lii » e drawn through the town of Tmckee and Washoe Peak. It consists principally of basalt ai d phom. lite. At Tahoe City a kind of glohnlifirous basalt occurs on the cliff just ncrth of the Tptst- office. The lower pait of it has been eroded by tbe waves ot the lake like a htndlar d on a eon- coast The rock is somewhat fennginons and much decomposed. It crumbles in the fingers. Near Taboo City porphyritic j> rauite, containing numerous crystals of white feldspar, is found. Compact bluish granite occurs at Observatory Point, which is a spur of the ridge projecting far into the lake. Beyond this point grny pbonolite extends along tho lake- shore for 2 miles or more. The leuiainder of the ridge consists of bluish basalt as far north as Boca, and stretching back from the lake for several miles. Various spurs diverge from this ridge. The crest lines are often dotted with turrets of basalt, and a vast amount of debris is strewed over their slopes. Near Wallace's ranch, 5 miles southeast of Truckee, I observed basalt similar to that on Lake Tahoe. A feature worth mentioning in connection with the geology of the Western summit is the absence of sedimentary rocks. No fossils are found by which one can determine the position of these arcbiean and igneous rocks in the geological series. In closing a report on the geology of Lake Tahoe and vicinity, a brief reference may be made to the lake as a rehoit for tourists aud pleasure- seekers. Since the completion of the Central Pacific and Virginia and Truckee Railroads, Lake Tahoe has become very accessible. A small steamer, carrying the mail, makes a daily tour of the lake. Theie is sufficient hotel accommodation for a large number of travelers. Rote 1* have l » ien erected at tbe following points on the hike: Hot Springs, Glenbrook, Kearney's, Rowland's, Yanks, McKinney's, and Tahoe City, The finest scenery is found in the southwestern corner of Lake Tahoe, near Tallac Peak. There is no part of ihe United States that surpasses this region in scenery. In my extensive travels on the continent of Europe 1 nave seen but one lake moie pictuiet> que than Tahoe, viz, the lake cf Luzerne, in Switzerland. Grace Greenwood, writing from California, says: IA Tahoe is tho mo- st beantiful lake I have ever beheld. * * * 1 think Lake Tahoe must yet become a great pleasure resort. 1 have seen no more charming spot in all my tours for a 8nminer's rest and rambling." Respectfully submitted. ALFRED R. CONKLING. Lieut. G. M. WHEELER, Corps of Engineers, in charge. APPENDIX H 1. REPORT ON THE LITHOLOOY OF PORTIONS OF SOUTHERN COLORADO, AND NORTHERN NEW MEXICO, BY A. 15. CONKLING. NEW YORK CITY, May 10,1677. SIR : I have tho honor to submit herewith a report on the lithology of the portions of Southern Colorado, and Northern New Mexico, explored by me in the field- season of 1875: The mnjority of the rocks occurring in this region are of igneous origin. They coyer large areas on both sides of the Spanish Range. The most common rocks are dolerite, basalt, granite, trachyte, diorite, granulite* sandstone and limestone. Dolerite occurs more frequently than any other species; vesicular dolerite covers large tracts of country, as in the plateau bounding the San Luis Valley on the west. Compact bluish dolerite is fonud in the biittes near Costilla post office, New Mexico, and in the mesa northeast of Fort Garland. Olivine Is fonnd in the dolerite at several localities. The basalt is usually of a blue color, and varies in texture from compact to scoriaceous. |