THE TECHNOLOGIST. [Nov. 1, 1864. 



174 QUICKSILVER MINES, ETC. 



with wood, and separated from the ore by a wall pierced with numerous 

 openings by the omission of bricks for that purpose. 



Connected with the furnace is a series of lofty and capacious 

 chambers, also of masonry, through which the whole product of com- 

 bustion is compelled to pass alternately above and below, from chamber 

 to chamber, until all the available mercury is condensed. The draught 

 from these furnaces is carried by inclined stacks up to the top of a lofty 

 hill several hundred feet distant ; and here the sulphurous and other effete 

 products of the furnace are discharged. Formerly no precautions were 

 taken to prevent the escape of mercury through the foundations of the 

 furnace to the earth beneath ; now the furnaces stand upon double arches 

 of brickwork, and plates of iron are built into the foundations, so as to 

 cut off entirely all descending particles of the metal and turn them 

 inward. To be convinced of the importance of this precaution, it is 

 sufficient to watch the operation of the furnace for a few moments, when 

 an intermittent stream may be seen to flow into into a reservoir provided 

 for it, and which by the former process was completely lost in the 

 earth. 



On taking up the foundations of some of the old furnaces within the 

 last two years, the metal was found to have penetrated, or rather per- 

 meated, completely through the foundation and clay of the substructure 

 down to the bed-rock beneath, a depth of not less than 25 or 30 feet. 

 Over 2,000 flasks of mercury were thus recovered in a single year from 

 the foundations of the two furnaces. This loss is entirely avoided by the 

 improved construction which has been adopted. 



The whole process of reduction is extremely simple, the time 

 occupied from one charge to another being usually about seven 

 days. The metal begins to run in from four to six hours after the fires 

 are lighted, and in about sixty hours the process is completed. The 

 metal is conducted through various condensing chambers by means of 

 pipes of iron to a " crane-neck," which discharges into capacious kettles. 

 It undergoes no further preparation for market, being quite clean from 

 all dross. 



Deducting two and a half years, during which the mines were in a 

 state of inactivity, pending the decision of the law-suit, the average 

 monthly product for twelve and a half years has been not far from 

 2,500 flasks, of 76J pounds each, of mercury. The selling price in San 

 Francisco is, at present, and has been for some time past, 75c. per pound, 

 while in London and New York it has ranged from 40c. to 50c. per 

 pound. 



