The
navigable waters affected by the mines are the bays of Suisun and San
Pablo and the Sacramento, San Joaquin, and Feather rivers. The smaller
and non-navigable streams which receive more or less of the sands are
(besides the Trinity and Klamath rivers, where so little washing is
done that they need not be considered): the American (tributary of the
Sacramento) in the north ; and the Merced, the Tuolumne, the
Stanislaus, the Calaveras, the Mokelumne, and the Cosumnes
(tributaries of the San Joaquin) in the south. The quantity of debris
which has been washed into these streams is unknown, and data based on
reconstructed topography in the mining regions are, from the nature of
the case, simply guesses. The only available method of estimating with
any approach to accuracy the amounts of material mined seems to be
that of taking the water used and averaging the duties of the inch, as
surveys of the washings are kept up only in exceptional cases.
The
inch differs as much as 20 per cent., the nature of the ground mined
continually changes, and the character of the sluices varies not only
in every district but in almost every claim. These estimates,
therefore, must be considered as the mean of many conjectures. It can
be safely stated that only in a few instances do any of the ditches
discharge the quantity of water which they are rated to deliver
according' to official statements or in the assessors' returns, from
which sources chiefly the cubic yards mined have been estimated.
The
following tables, XXIX. and XXX., are based on this method. Table XXIX.
is from William Hammond Hall, State Engineer, Report of 1880, part iii.
p. 24. Table XXX. is from Lieutenant-Colonel G. H. Mendell's Report
upon Mining Debris in California Rivers, 1882., p. 15:
