28 ECONOMIC GEOLOGY, 
Hydraulic processes have been thoroughly perfected in California. 
Canals, many miles in length and passing over ravines 200 feet deep, 
have been constructed to convey the water, so that by a large hose-pipe 
it may be brought to bear upon the auriferous gravel in the right place. 
That gravel is commonly as hard as rock, the pebbles being too firmly set 
to be broken apart by hand. Detailed descriptions of the processes are 
unnecessary; but I will mention the cost of excavation in different parts 
of the country, as presented by several experts. Prof. W. P. Blake esti- 
tated, from work done in North Carolina in 1859, that earth containing 
only the twenty-fifth part of a grain of gold, or two mills’ worth in a 
bushel, will pay about two dollars a day to a single pipe. In California, 
about 1868, the same gentleman estimated that, with certain conven- 
iences described, 1,500 tons of earth could be removed in a day’s time 
with the labor of two men. This result has been actually obtained 
there under favorable circumstances. 
M. Laur, a French engineer, estimating miners’ wages at twenty francs 
($3.68) per day, found that the expense of manual labor necessary for 
working one cubic metre (38 inches) of gravel by the several methods to 
be the following: By the pan, about $13.80; by the rocker, about $3.68; 
by the long tom, about $0.92; by the sluice, about $0.31; by hydraulic 
washing, about $0.051. This would make the cost of a cubic yard about 
five cents. These estimates include the cost of the water. 
The cost of hydraulic mining in our state ought not to be greater than 
in California. These estimates do not cover the cost of the canals and 
apparatus, though they do include the rents paid for the water, or the 
interest upon the capital. The profit arising from the employment of the 
hydraulic processes must depend upon the richness of the gravel and the 
expense of uncovering the “pay dirt.” In Canada, as already stated, and 
in Vermont, the hydraulic methods have been employed successfully 
within the past dozen years. 
Can GoLp-MINING BE MADE PROFITABLE IN NEw HampsHIRE? 
We now possess the data needful to enable us to answer this question. 
After ten years’ intimate acquaintance with all that has been done in the 
way of mining and milling gold in our state, I am satisfied that this busi- 
ness, if properly conducted, cannot fail to be remunerative. This is not 
