116 Journal of the Mitchell Society [. November 
bottom of the troughs, which allows the formation of a bed 
of stones, which reduces the wear on the bottom and helps 
save the gold. This bed of stones is of course more or less 
shaken up by blows from the large fragments of quartz and 
by the revolving arms, thus permitting the gold to settle 
through as in panning. The constant striking of the paddles 
against the surface of the water will also weight and sink 
some of the float gold. The discharge end of the machine is 
set 6 inches higher than the feed end so that the gold, once 
down amongst the pebbles of the bed, is not apt to be pushed 
out. 
Riffles of the sluices are made 'by boring inclined auger 
holes in the planks laid lengthwise in the cement-lined sluice 
boxes. Since all the coarse gravel has been screened out, 
there is little wear upon the riffles and the fall and quantity of 
water are less than in the regular sluice for hydraulic mining. 
In cleaning up, the planks are lifted up and turned over and 
the gravel and mercury washed to the end of the sluice where 
quicksilver and amalgam are washed out in hand pans. 
When through cleaning up, the planks are simply replaced 
and the riffles filled with mercury and the machine started 
again. 
In cleaning the washers, which is usually done twice a week 
the machines are stopped and all the gravel within washed 
out with a hose through an opening in the bottom. This 
gravel is then panned by hand and the gold amalgamated. 
Any nuggets that occur in the rock are pounded free from 
quartz and are then also amalgamated. 
The amalgam from all sources is strained out of the quick- 
silver and then retorted and the bullion sold. 
The chief wear on the machine is the arms, which under 
certain conditions, as on the sharp ore at the Shuford mine, 
only last six weeks. They can, however, be readily made at 
any foundry. 
It is recommended by the maker that the first washer be 
driven at 150 to 250 revolutions per minute and that the second 
one at 250 to 350 per minute and that for a capacity of 10 tons 
