30 ft. or more. The clay is often seen to be but partially decomposed slate, still retaining the structure of this rock, which was evidently the matrix of the gold.—The general gold formation of California is found in the neighboring states and territories, the entire territories of the United States west of the Rocky mountains being more or less productive. In many parts of this region valuable mines are already worked, and here is little doubt that some of them may in the future contribute more than California to the general gold production of the country. In Nevada gold has been obtained from the quartz and from placers, but the product of the state has been chiefly derived from the auriferous silver ores of the great Comstock vein, discovered in 1859, which yields about one third gold and two thirds silver. Gold has been obtained from Oregon since 1850, and the recent production has been roughly estimated at about $2,000,000 annually. It was first discovered in Washington territory on the E. slope of the Cascade mountains in 1858. The gold region was traced along the upper Columbia and its tributaries, and in 1860 it was found on the W. slope of the Bitter Root mountains, now in Idaho. There are gold washings in almost all parts of Idaho; the gold contains more silver than that of California, and averages about .760. In Montana there are extensive placers and quartz veins, on the E. slopes of the Bitter Root mountains, and on both sides of the Rocky mountain chain, at the sources of the Missouri river. In Colorado gold occurs in lodes or fissure veins, in a belt about 50 m. wide, extending over the central portion of the territory N. and S. (See Colorado.) Gold is also obtained from Utah and Arizona, and is known to exist in Dakota. The auriferous belt of Oregon, and of Idaho, Montana, and Washington territories, extends N. along the slopes of the Rocky mountain chain into British Columbia. The mining of gold in this latter country dates from 1858, though the existence of the metal had been announced in 1856. Gold has been found on the Fraser river from a point about 45 m. from its mouth to its source in the Rocky mountains, a distance of upward of 700 m. by the meanderings of the river. It is also found on many tributaries of the Fraser and on Vancouver island. The fields which have been most extensively worked are in the Caribou district, which lies in the N. bend of the Fraser. N. of this district placers have been discovered on Peace river, and still further N. on the Stickeen, which empties into the Pacific S. of Sitka, near lat. 55°. The metal has also been found above that point, but in small quantities. The greater part of the gold from British Columbia is obtained from shallow placers. The production is sent to San Francisco; it amounted in 1873 to $1,250,035. (See British Columbia.)—In the province of Ontario, Canada, gold has been found in small irregular deposits of considerable richness in Madoc. The gangue of the gold was in part a ferriferous bitter spar, and in part a peculiar hydrocarbonaceous coaly matter, the two being associated in the same veins, and alike penetrated by crystalline gold of great purity. The adjacent township of Marmora has since been found to contain gold in quartz veins with mispickel. Though not rich, the ore is abundant, and the deposits there are now worked on a considerable scale. The rocks of this region are crystalline schists, probably of Huronian age; and rich gold-bearing veins have recently been discovered in rocks of the same period N. of Lake Superior, on Lake Shebandowan. For many years the gold-bearing alluvions of the Chaudière and the adjacent region in the province of Quebec have attracted attention, and have yielded more or less gold. It is distributed over a large area, but the official returns in 1869 show a production of only 1,050 oz. from the Chaudière valley, although small quantities are extracted in various other localities in the region. The source of the gold appears to be in part in the adjacent crystalline rocks of Huronian age, and in part in some argillites and sandstones which are perhaps of the lower Cambrian period, but may be more recent. In both of these formations, native gold accompanied with sulphurets occurs in quartz veins, which have not however as yet been systematically worked. In Nova Scotia the auriferous quartz occurs in uncrystalline slates and sandstones, for the most part in interbedded veins. The workings have been on a small scale and very irregular, but the quartz is often of great richness. The official returns from 1860 to 1872 show a yield of 215,871 oz., with a value of £863,484. The produce in 1867 was 27,314 oz., but in 1872 only 13,094 oz.—The gold-producing districts of South America are in Brazil, Chili, and all those countries which lie north of the latter on the line of the Andes. As in Europe and Asia, it is the N. and S. ranges of hills of micaceous and talcose slates, quartz rocks, and granites, which produce this metal. In some instances, as in Peru and Chili, it is obtained from veins commonly worked for other metals as well as gold; but almost universally it is a product of alluvial mines. The yield since the early working of the mines has greatly fallen off, and especially since the commencement of the present century; and South America, from having been the first of the gold-producing countries in the world, has now fallen among those of least importance in this respect. Still it is well known that there are districts of great richness yet comparatively unworked, and which are likely long to continue so from their extreme unhealthiness and the want of means of comfortable subsistence. Such is the country about the head waters of the Atrato, the Magdalena, and the Cauca. Similar causes, as well as the political condition of the countries of Central America, have prevented the development of their resources in this metal, which it is well known follows the Cordilleras northward. On the isthmus of Panama discoveries of images
