328 RESOURCES OP CALIFORNIA. 



have usually formed either oxydes or oxychlorides of all the 

 base metals in the ore treated, leaving gold as the only 

 free metal to absorb the chlorine gas. In order to be sucess- 

 ful in roasting the ore, attention must be given to the construc- 

 tion of the furnace. If the arch over the hearth is too high, the 

 ore will not be oxydized ; so also if the flues are too large, or 

 the damper is opened too wide, as the excess of cold air or 

 draft cools the ore. Then again, if the arch is too low, or flues 

 too small, the air will fail to yield its oxygen to desulphurize and 

 oxydize the ore. Cold air must always flow into the furnace 

 through the work-holes, but it must be in proper quantities 

 and the work-holes must be in proportion to the chimney-flues. 

 The main principle of chlorination is, that the metallic gold is 

 dissolved by chlorine gas, while metallic oxydes are left un- 

 touched. The ore is first roasted in a furnace of proper con- 

 struction, and then enclosed in a covered vat, into which 

 chlorine gas is introduced, until all the gold is converted into 

 chloride of gold ; and then the vat is opened and filled with 

 water, which dissolves the gold as sugar is dissolved under sim- 

 ilar circumstances. The solution is drawn off, and the metal- 

 lic gold precipitated from it by the introduction of the proto- 

 sulphate of iron. The cost of the entire process does not ex- 

 ceed $20 per ton ; and in some locations, where wood is cheap 

 and freights moderate, it may be worked as low as $1 2 per ton 

 of sulphurets. The roasting is the most difficult step in the 

 entire process, but every part must be correctly performed. 



253. Quicksilver. The productive quicksilver mines of 

 California are all in the Coast Mountains, between latitudes 

 36 s and 39. There are three main groups : those of Santa 

 Clara County, including the New Almaden, which produces 

 11,000 flasks annually ; those of Fresno, including the New 

 Idria, which yields about 6,000 ; and those of Napa, including 

 the Redington, producing 7,000. The yield is irregular 

 in all the districts and all the mines, the ore being found in 

 masses almost disconnected ; so that the working of a good 

 body of cinnabar in one year may be followed by several 



