276 COSTS OF WORKING AND THE YIELD OF GRAVEL.
of
these were collected and printed in the reports of the U. S.
Commissioner of Mining Statistics, and Prof. Whitney has added to them
in his " Contributions to American Geology." Detailed investigations
have been undertaken of late by the State Engineer of California and
also by Lieutenant-Colonel Mendell, Corps of Engineers, U. S. A.
There
is now obtainable quite a large amount of statistics in printed form;
but to a great extent these are of no value, partly from their
unreliability, partly from their insufficiency of detail. Miners and
mining corporations as a rule object to making public anything
concerning their property except what is -absolutely necessary, and are
apt, when pressed, to give ambiguous information. As it is impossible,
after large areas of ground have been washed away, to accurately
reconstruct their topography, all statistics of the cubic contents of
excavations derived from surveys made after mining has ceased are
unreliable.
The
most reliable data are those of the North Bloom-field and the La Grange
Hydraulic Companies, both of which have carried on their works in the
most intelligent and satisfactory manner.
To
better familiarize the reader with the subject of gravel-mining, and
thus enable him to form an idea of the amount of water used per cubic
yard of dirt moved, and of the corresponding yield and attendant costs,
an exhibit of a claim running on an approximately minimum basis—viz.,
light pressures and smallest practicable grades—has been selected. For
this purpose the claims of the La Grange Company have been chosen, as
the yield per cubic yard and the grades there used can be considered as
nearly the lightest with which an hydraulic claim can yield
remunerative returns.
The annexed tabular statements show in convenient form the data alluded to.* The tables have been care-
*
In obtaining the data for these tables I am greatly indebted to the
valuable assistance of Mr. Joseph Messerer, superintendent of the La
Grange Ditch and Hydraulic Mining Company.
