258 REPORTS FROM THE SECTIONS. 
In America the water holding these slimes in suspension is run 
into large settling ponds, three or four ounces of alum is added 
for each thousand gallons of liquid, and the whole is left at rest 
until the water is perfectly clear, the clarification being much 
hastened by the alum 
In the United States the richer silver ores containing over 80oz. 
per ton are eg dry, roasted with from five to ten per cent. of 
salt, and treated by amalgamation in barrels with scrap iron. 
The poorer ores, especially in places where fuel is scarce, are 
treated a a Feng method, based on the same principle as the 
patio process of Mexico jnamely, that chloride of copper in presence 
of salt nner sulphide of silver into chloride. In Nevada, how- 
ever, the process is hastened by artificial heat, and the reduction 
of the chloride of silver instead of being effected by mercury, 18 
effected at the expense of the iron of the grinding pans. 
under — the whole material being saved, and 1,250 to 
1,500ibs. of the sand is ground to an impalpable powder in @ 
ler pan, which takes about an hour. The contents of the 
pan are then heated to about 200°F. by steam, taking care not to 
allow the condensed water to dilute the mud to “too great an 
extent, and 10 to 15% of the weight of the ore of mercury is 
~ sh into the pan by pressing it through a canvas bag. Two 
pounds of Te of copper and three pounds of salt or -_ 
rich tin deposits ts lying almost on the surface. Many of the ores 
which have been worked for gold, notably about Mitchell’s creek, 
contain much silver, and doubtless in treating fo r gold a great 
