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78 gold, and of Oregon also, was noticed by Prof. J. D. Dana, and recorded in his geological report of the country. In Hunt's “Merchants' Magazine” for April, 1847, is a very decided statement by Mr. Sloat respecting the richness of the country in gold, made from his observations there the two preceding years; and he confidently predicts that its mineral developments will greatly exceed in richness and variety the most sanguine expectations. In these years the Mormons connected with the army were known to have gathered some gold upon the banks of the streams, and the Mexicans and Indians also. A party of three Americans, two of them Mormons, were on Feb. 9, 1848, at Sutter's mill on the American fork of the Sacramento, near the town of Coloma in El Dorado co., engaged in repairing the race, which had been damaged by the spring freshets, when the little daughter of the overseer, named Marshall, picked up in the race a lump of gold and showed it to her father as a pretty stone. The discovery did not immediately attract much attention; and the Mormons particularly sought to prevent the facts from being made public. The Rev. C. S. Lyman, in a letter to the “American Journal of Science,” of March, 1848, says: “Gold has been found recently on the Sacramento near Sutter's fort. It occurs in small masses in the sands of a new mill race, and is said to promise well.” The news spread rapidly, and caused an unparalleled tide of emigration to pour in from Mexico, South America, the Atlantic states, and even from Europe and China. (See .) In August of that year Governor Mason reported 4,000 men engaged in working gold, and a daily product of the value of $30,000 to $50,000. The earlier diggings were mostly deposits resting upon the upturned edges of argillaceous slates, the gold being found entangled in these under the sand and gravel, and also more or less mixed through the superficial layers. A large proportion was picked out by hand at many of the diggings, so abundant were the coarse pieces. Attention was early directed to the gold veins, and in 1851 regular quartz mining was commenced at Spring Hill in Amador co. In 1857 numerous mills, most complete and thorough in their construction, were in operation over a great part of the country; and mines were opened at greater depths than gold is often worked in other countries. A shaft of the Mount Hope mining company in Grass Valley was carried to the depth of 241 ft., reaching the vein at 350 ft. following its slope, and the richness of the veinstone at this depth gave full encouragement to the belief that these repositories were permanent and inexhaustible. Many other mines were worked from 150 to 200 ft. in depth. In California, though gold is found E. of the Sierra Nevada, among the mountains of the coast, and in various other localities, the great gold region is on the W. slope of the Sierra, and extends from about lat. 35° N. northerly

to Oregon, a distance of about 500 m. The average breadth of this gold belt is about 40 m. The principal mining operations have been confined to a central area extending N. and S. about 220 m., between the parallels of 37° and 40°, and embracing Mariposa, Tuolumne, Calaveras, Amador, El Dorado, Placer, Nevada, Sierra, Yuba, Butte, and Plumas counties. According to William P. Blake, gold-bearing veins on the W. slope of the Sierra Nevada occur in or are closely associated with clay s t l ates, sandstones, and conglomerates of the secondary period; also in hard and compact granite, in greenstone or dioritic rocks, and in dolomite and metamorphic limestones. In the Coast mountains they are found even in the partially metamorphosed stratified formations of the cretaceous period. The largest and most extensive veins exist in the region of the metamorphosed secondary rocks, varying in width from a few inches to 20 or 30 ft., and generally conforming to the dip and strike of the strata. “The most extensive vein of the state,” says Mr. Blake, “and perhaps in the world, is known among the miners as the ‘mother vein,’ and extends, but with some considerable, breaks and interruptions, from Mariposa northwestward for 80 or 100 m., following a zone or belt of Jurassic slates and sandstones, and closely associated with a stratum of dolomite or magnesian rock, often a magnesite, filled with reticulations of quartz veins and charged with pyrites.” The chief production of California gold has been obtained from placers. The great placer region extends over the central counties from Mariposa to Butte. The deposits occur not only in the beds of the streams, but also upon the hillsides and tops, where ancient watercourses are supposed to have been. Sometimes they are found under enormous accumulations of sand, clay, gravel, and even of tufa and lava; the smoothly worn stones are thoroughly cemented together, and form a solid conglomerate or “cement;” the auriferous deposits consist of gravel and bowlders, varying in size from a grain of wheat to masses weighing many tons. These hills on the W. slope of the Sierra Nevada cover a tract of country in places 50 to 60 m. in width, and rise sometimes to the height of 4,000 ft. They are traversed by numerous streams, whose sources are in the Sierra Nevada. Subject to sudden and extreme freshets from the melting of the snows and from the long continued rains of the wet season, these streams excavate and sweep down the loosely aggregated rocks, and wear deep cañons and gulches, which extend toward the valleys of the Sacramento and San Joaquin. Thus it was the same agency which impressed this peculiar feature upon the topography of the region, and spread the gold from the veins in the hills through the ravines and down into the valleys. Even upon the elevated plains quite to the west of the hills gold is collected in strata of sand and clayey deposits, which cover the surface to the depth of 15 to