MINES 287 



flank of the continuation of the great chain of mountains which we have traced up- 

 wards from South America. 



Almost the entire quantity of the gold produced in California is obtained from 

 stream-works, washings, or ' diggings,' but the precious metal itself has evidently been 

 derived from veins in the- granitic and the ancient slaty rocks which constitute the 

 range of the Sierra Nevada. The alluvial deposits occupying ancient river-courses 

 are termed ' deep placers,' whilst those which have been re-distributed, and lie near the 

 surface, are called ' shallow placers.' The gold-bearing gravels are usually worked by 

 a process known as ' hydraulic mining.' See GOLD. Platinum and osmiridium have 

 also been found here. 



The auriferous tracts extend northward far into the British territory, and are 

 worked in British Columbia. 



In one of the side valleys of San Jose, a mine of quicksilver, ' New Almaden,' has 

 for some years been opened upon irregular and contorted deposits of cinnabar, asso- 

 ciated with clay-slates highly inclined and similarly contorted. It is said that above 

 10,000 cwts. of mercury are produced here annually. 



On the eastern or Atlantic side of the North American continent, the existence of 

 gold has long been known, as well in alluvium in Virginia, Carolina, Georgia, and 

 Canada, as in veins which occur at intervals in the schist rocks of the Appalachian 

 chain, and which have given rise to numerous explorations. 



The veins appear generally to course NN.E. and SS.W., and to consist mainly of 

 quartz, often extending to a great thickness. Few, however, of these mines have been 

 followed down to a depth of more than 100 feet, or have been developed on a con- 

 tinuously large scale. 



Lead mines have bean worked in distinct veins at Rossie, St. Lawrence County, N.Y., 

 at Shelburne in New Hampshire, Southampton and Northampton, in Massachusetts, 

 Middleton, Connecticut, Chester County, and Wheatley mines, Pennsylvania ; but the 

 most important are those opened in irregular deposits sometimes vertical, at others 

 horizontal, which distinguish the Silurian limestones of the Upper Mississippi. The 

 lead-bearing region is 87 miles long from east to west, and 54 miles broad from north 

 to south, the chief centres being Galena, Mineral Point, and Dubuque. The ore, 

 generally pure galena, occurs with great irregularity. It occupies only one zone, about 

 100 feet in thickness, of the 'galena' limestone, and hence the mines have been but 

 shallow. In Missouri an analogous state of things occurs. Copper has been worked 

 at several mines in the Atlantic States, in Maryland ; in New Jersey ; several localities 

 in Tennessee ; andPerkiomen in Pennsylvania, where the veins occur in new red sand- 

 stone and shale. 



In 1841 Mr. Doughton, state geologist for Michigan, first drew public attention to 

 the native copper of Lake Superior, which has been the object of very numerous 

 workings, and has been produced in steadily increasing quantity. 



The copper occurs in a district of bedded augitic trap, amygdaloid, and sandstone, 

 with conglomerate of the lower Silurian period, and the rocks are especially remark- 

 able for bearing native copper with but little of the ordinary ores of that metal. 



Ores of zinc are associated with lead ores at several of the above-mentioned localities, 

 especially in the Wisconsin district, where the calamine is known among the miners 

 by the name of ' dry-bone.' But one of the most peculiar mineral deposits in the 

 United States is that of the red oxide of zinc, and of Franklinite, which occur in 

 Sussex County, New Jersey, at Sparta and Stirling. They are intercalated among 

 the beds of a crystalline limestone, with a total thickness of above 30 feet, and are tho 

 scene of very successful undertakings. 



Lastly, iron ores of various species, particularly the magnetic oxide and haematite, 

 occur in numerous localities, Missouri is remarkable for large masses, and Lake 

 Superior offers even a greater abundance. 



A bed of magnetic oxide of iron occurs in gneiss nea^ Franconia in New Hampshire. 

 It has a width of from 5 to 8 feet ; and has been mined through a length of 200 feet, 

 and to a depth of 90 feet. Tho same ore is found in veins in Massachusets and Ver- 

 mont, accompanied by copper and iron pyrites. It is met with in immense quantities 

 on the western bank of the lake Champlain, forming beds of from 1 to 20 feet in thick- 

 ness, almost without mixture, encased in granite. It is also found in the mountains of 

 that territory. These deposits appear to extend without interruption from Canada 

 to the neighbourhood of New York, where an exploration on them may be seen at 

 Crown-Point. The ore there extracted is in much esteem. Several mines of the 

 same species exist in New Jersey. The primary mountains which rise in the north 

 of this state near the Delaware, include beds almost vertical of black oxide of iron, 

 which have been worked to 100 feet in depth. In the county of Sussex the same ore 

 occurs, accompanied with Franklinite. At Eoxbury, in Connecticut, a good sized 

 lode of sparry iron occurs ; the only one of the kind known in tho Alleghanies. 



