1868. | Gold in California. 319 
Beyond the blankets are troughs lined with amalgamated sheet- 
copper, to retain any light particles of gold that might otherwise 
escape; these again terminate in settling-pits, or tyes, in which a 
portion of the sand and the greater part of the auriferous pyrites 
are collected. 
The gold and other heavy materials collected in the vats in 
which the blanket-washing is carried on, are afterwards passed 
through the amalgamator. This machine consists of two wooden 
rollers, about eight inches in diameter and two feet in length, fur- 
nished, on their circumference, with knife-bladed pieces of iron 
arranged around them with their edges at right angles to the cylin- 
ders, and working in cisterns containing mercury. Above these 
rollers, which are set in motion by belts, both im the same direction, 
but contrary to the course of the water flowing through the appa- 
ratus, is a hopper for receiving the sand to be washed. Below the 
cylinder is a “riffle-board,” having an inclination of about seven 
degrees from the horizontal, and generally covered by plates of amal- 
gamated copper, which can be readily slipped out for the purpose of 
haying the gold amalgam which may have become attached to them 
scraped off. When copper plates are not employed for this purpose, 
the transverse grooves of the riffles are charged with mercury. To 
use this apparatus some of the sand, taken from the cisterns in 
which the blankets have been washed, is placed in the hopper, 
and a small stream of slightly warm water allowed to play on it, 
in such a way as to gradually wash it under the revolving spiked 
cylinders, and from thence over the amalgamated riffles. The 
riffle-board is usually nine feet in length, is divided by nbs into 
several channels, and has, at its lower extremity, a cistern for re- 
taining the pyrites, which, not combining with mercury, escapes 
amalgamation. 
The sulphides thus collected are sometimes ground with mercury 
in a small arrastre, or edge-mill, and, after extracting from them as 
much gold as can be thus obtained, they may, if they still retain a 
sufficient amount of the precious metal, be drawn off, and, after 
settling, be collected and sold for treatment by chlorination, or smelt- 
ing with lead ore. 
The quicksilver drawn off from the amalgamator is first strained, 
either through close canvas or buckskin, the solid amalgam is dis- 
tilled in a cast-iron retort, and the gold fused in blacklead crucibles, 
and then cast into ingots. 
The auriferous pyrites is concentrated by washing, and when 
the chlorination process is employed, it is subsequently roasted 
“dead” in a reverberatory furnace, and afterwards subjected, in a 
moist state, to the action of chlorine gas. Chloride of gold is sub- 
sequently washed out with hot water, the gold precipitated by sul- 
phate of iron, and then run into bars in the usual way. 
