368 RESUME AND THEORETICAL DISCUSSION. 
to $63,000,000 in value, or in round numbers at from 250,000 to 260,000 
pound, Troy in weight. The present yield —that is, the average yield of 
the last few years — has been much less than that. At the beginning of the 
present decennium, it was probably about $20,000,000 in value, and since 
that time has slowly and irregularly decreased, the present production 
being about $18,000,000. Considerably the larger portion of this comes 
from the hydraulic and tunnel mines, chiefly from the former. The best 
authorities estimate the present yield from this source at from $12,000,000 
to $ 14,000,000. 
It would be extremely desirable to be able to state how much has been 
expended in obtaining this amount of gold by the hydraulic method. This, 
however, is entirely impossible. The most that can be done is, to give 
approximate figures for a few localities where circumstances have been 
especially favorable for collecting information. An ideal report on the 
hydraulic mining business, from the economical side, would furnish infor- 
mation on the following points, for each district or special locality investi- 
gated: the total yield; the yield per cubic yard of material washed ;* the 
cost of obtaining the gold, as divided between the various items of water, 
materials expended, labor, and interest of capital employed; the amount of 
water used and of gravel moved by this water. Such information as this 
would be of value for each locality, and as much as could be collected in the 
various districts visited in the course of our work kas been presented in the 
present volume. It must, however, be impressed upon the reader that 
averages drawn from these statements have little value as a practical guide 
to those desirous of embarking in the business of hydraulic mining. The 
conditions are so complicated that each special district must be judged by 
itself, each circumstance influencing production being taken separately into 
account. Hence, it will be apparent that the figures professing to give the 
average yield of the gravel in the Sierra Nevada, and the average amount 
made per diem by the miners in working it, are entirely worthless This 
* The cubic yard is universally employed as the unit of quantity in the hydraulic mining region, and the pro- 
duce is stated in values not in weights. Taking gold at $18.50 per ounce, the cent’s worth would be equal to 
a little over a quarter of a grain in weight of the metal (0.2594 gr.). 
+ The estimates of average yield and profit in working the auriferous gravels of California, by various methods, 
which have been most widely circulated and credited, are those emanating from M. Laur, and are extracted from 
his report to the French Government, published in 1862. They are the merest guesses of a person of no experi- 
ence, who had paid a flying visit to two or three localities of hydraulic mining, —a business at that time quite in 
its infancy. They are of a piece with his tabular statement of the daily average amount earned by each miner 
during the earlier years of placer mining, at a time when, in point of fact, the number of men at work is not 
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