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Show 47 lieved, will furnish information regarding the same heretofore bat mea-gerlj known. Attached to his report is a list of the rock and mineral specimens collected by himself and Mr. Conkling. He also submits a report on the chemical composition of the alkaline lakes, thermal and mineral springs of Southern California met with during the season. ( See Appendixes H 2 and H 3.) Mr. Gonkling submits a report on the geology of the mountain ranges from La Veta Pass to the head of the Pecos Biver. ( See Appendix H 4.) Paleontology.- Collections in this branch were made by Prof. Jules Marcou and Messrs. A. R. ConklingandD. A. Joy, which have received a preliminary examination only. Whenever the necessary facilities will allow an analytical examination and report upon them will be made. MINING DEFORMATION. As in the preceding years, examinations into the general character, condition, & c, of mining districts and mines located within the areas entered by parties of the expedition have been made, and the following is a condensation from the results of the investigations for 1875-' 76 of mines located in California, Nevada, Colorado, New Mexico, and Arizona. BLIND SPRING DISTRICT, CALIFORNIA. Examined by Dr. 0. Loew, October, 1875. The mines of this district are in the Blind Spring Mountains, an isolated range about eight miles long and three and a half wide, which lies between the Sierra Blanca and Sierra Nevada. The trend of its longer axis is north and south, following the direction of the mountains. Its croppings cover a large area, approximately 7,000 acres. Benton is the post- office. The nearest railway town is Carson, Nev., one hundred and sixty- five miles distant, with which it is connected by a freight and stage line. The roads in the neighborhood tire through deep sand. This district was discovered in 1865, organized in the same year, and has been worked continuously since. In 1871, a geological investigation was made by Dr. Hoffman of this survey. The direction of the lodes is north and south. The wall- rock is of granite. In the vicinity the azoic formation prevails. The main ores are argentiferous galena and argentiferous copper glance 5 but these are accompanied by other valuable minerals in large and small quantities, among which are partzite- a very rare silver ore, stetefeld-tite, cerussite, malachite, cerargyrite, and chrysocolla. These metallic combinations are imbedded in masses in the ledge matter, which consists of ferruginous clay and quartzites, and varies in width from 3 to 8 feet. Among the base ores, iron pyrites, cuprite, and zincblende in large and well- formed crystals occur. Indications of gold, varying from a trace up to $ 5 per ton, are found. Some of the ores are treated by direct milling; others are previously roasted. Salt is added to the ores in roasting in order to convert, the sulphates into chlorides; the escaping gases and fumes have a strong odor of sulphurous chloride. The water- level has not yet been reached. The Comanche is the principal lode. It is a ledge of clay and quartzite from 3 to 8 feet wide, through which the ore is distributed. Its direction is north and south. The dip is 73°. It is between smooth granite walls, apparently |