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Show 1286 . REPORT OP THE CHIEF OF ENGINEERS. the ground filled with this thermal water. Both these springs contain sulphereted hydrogen, a gas generally evolved in the fissures of rock in a volcanic region. At Genoa, 14 miles south of Carson, and near Franktown, 10 miles north of the same place, warm springs occur. Both houses and hotels have been built at both Ibese localities. I was unable to learn the temperature of either of these thermal waters. I collected qnarc bottles full of water from the above springs for analysis, but upon reaching Washington it was found that either the rold weather or careless treatment in transportation had resulted in the breakage of the bottles and consequent loss of contents. The greater part of the Carson Valley belougs to the Quaternary, and there is very little rock in situ, excepting on the eastern side of the valley, where a few minor ridges and buttes of basalt occur. The line of upheaval in these ridges is north and south. Beginning on the north, we have a low range of gray granite, which contains numerous crystals of black hornblende, and separates Washoe Valley from the Car- Ron Valley. Rocky tors of granite outorop in various places on this divide. The North Carson Mine occurs in this ridge, but for a description of it see chapter on mines. At Swift's Spring, sty miles northeast of Carson, a ledge of gray mica slate outcrops. This is the only locality in tne valley where a niet amorphic rock is found. I did not find the continuation of the mica- slate beds. Olivine incrusts a low ridge of diorite about 50 feet high and a quarter of a mile long in the eastern part of the Carson Valley. A mass of granular yellow sandstone about 30 feet thick outcrops at a point a mile east of Carson. This'sandbtone is underlaid by clay, and apparently does not cover more than an acre. Invertebrate fossils are common in the rock, particularly the genus Unut, which is oftentimes stained by the oxide of iron. Vertebrate remains have also been found, but I was nnable to obtain any. Blaok mica is sparingly disseminated through the sandstone. The rock is extensively quarried by the inmates of the State prison, and is much used for building purposes. The State- house aud railway shops of the Virginia and Truckee Railroad are construe ted of this sandstone. Buttes of gray basalt, with a porphyritic texture, are found a short distance east and southeast of the State prison. The Como Mountains form the eastern bonndary of the Carson Valley. They are composed of trachyte- porphyry. The height of this range is about 8,500 feet. A bed of soft grny limestone, having a compact texture, occurs near Dayton, and a l> cd of bine limestone is found near the stage- road about half- way between Carson City aid Clear Creek. This rock is burned in kilns at both localities, but I was nnable to examine either of the deposits of limestone, and hence cannot state the thickness or dip of the strata. A bed of lignite occurs about 8 miles due east of the Carson Valley. It lies in the El Dorado Cafion, on the line of Oriusby and Lyon Couuties. The locality is known ae the Virginia City Company's Coal- mine. A good wagon- road from Dayton renders the mine easy of acce.- s. This lignite was discovered by English miners soon after the finding of the Comstock Lode. Prior to 18( 55,9,^* 00 tons of brown coal were exported from the mine, and under the incorporation of 1872, 21,600 tons were taken out, making a total of 31,400 tons since the formal opening of the mine. After 1803 the Virginia City Company suspended work for about eight years. Out of the 31,400 tons which the mine has yielded, 13,800 tons have been burned in Storey County, and the balance at the company's hoisting- works. The amount of money expended since the re- iucorporation of 1872 is f 110,000, and previous to that time about the same sum, making in round numbers the total cost, of working the mine $ 220,000. 1 visited this deposit of lignite in the El Dorado Cufiou on November V0, 1876, in company with Prof. W. F. Stewart and Mr. R. M. Daggett, the superintendent of the compauy. The object of our visit was to select a spot for the sinking of a new shaft. After some consultation a locality was decided upon about 1,200 feet southwest of the present hoisting- works. Professor Stewart has described the lignite beds in detail, and I condense from his report the following: " The coal indications in Western Nevada generally appear in the Tertiary. There is reason to believe that the El Dorado lignite belongs to this age. Toe mine lies near the bead of the csfion. There are two shafts, called respectively the Virginia and Newcastle. The former shaft is 420 feet deep, and is the one most used, as the hoisting- works are at the mouth of it, while the latter one is hot 85 feet deep and is now full of water. For about 300 feet from the surface the formation consists of alternating layers of marl, soft gray saudstones, shales, fire- clay, carbonized vegetable matter, and beds of weathered lignite. Below this is pudding- stone or bowlder clay, There are three veins of lignite, which are, counting from the surface, respectively 16 feet, 15 feet, and 6 to 8 feet in thickness. Bowlders and volcanic ashes occur between the veins. Pyrite is found with the lignite in the form of cubes. In making a section across the lignito beds from southeast to northwest we have firJt granite, then the miscellaneous formation containing the veins of lignite, then a dike of basalt, next sedimentary strata referred to the Tertiary, and filially an extensive mass of trachyte, which covers the country for Beveral miles." |