GEOLOGICAL SOCIETY- 



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in the residuum coming out of the last bowl, by simple 

 washing in the pan ; but it is to be found by the fire 

 assay. This undoubtedly arises from the sulphuret 

 which passes over with ground matter, and which sul- 

 phuret contains gold. 



The disadvantage of this process consists in the rapidity 

 with which the wet stamps are worn away and destroy- 

 ed, the best seldom lasting longer, so as to be useful, 

 than three weeks ; each wet stamp is considered to 

 stamp up 10 bushels or cwts. per day of 24 hours. It 

 is not maintained as yet that they fail by this process in 

 obtaining all the gold visible to the naked eye. 



The process of dry stamping and amalgamating by the 

 arrastre, as at El Oro and Guanaxuato, in Mexico, has 

 also been in use. 



The arrastre, in Mexico, is considered to amalga- 

 mate from 13 to 15 cwts. in the 24 hours. It is well 

 established that all the gold visible to the naked eye, by 

 the most minute pounding in a mortar, and afterwards 

 washing by hand, is to be obtained thus, but at a serious 

 loss in quicksilver; a loss partly caused by the continual 

 attrition of the quicksilver, and its consequent oxida- 

 tion. 



The Chilian mill has also been in vogue, but has given 

 way to the wet stamp and arrastre processes ; smelting 

 has not yet been systematically attempted. Thus have 

 been briefly described the processes in use in the United 

 States. 



Whether the wet stamps or the arrastre will be uni- 

 versally in use, is a question which experience and 

 "time will show. 



