The
average duty of the miner's inch in the deposits mined and discharged
into the San Joaquin and its tributaries, according to Lieutenant A.
W. Payson, Corps of Engineers, U. S. A., is shown in Table XXXIX.
In
discussing the subject Lieutenant Payson says: " I have thought it fair
to allow for the larger hydraulic mines 2^ yards per inch ; for the '
Jenny Lind ' and many of the smaller claims with low banks, deficient
head, grade, and water-supply, 2 yards; while in numerous instances of
placer, river, and drift mining, where excavated material is thrown
into sluice-boxes, I have varied the amounts according to my knowledge
of the circumstances. . . . The quantity for Calaveras is based on the
probable future water-supply."
From empirical data at the Jenny Lind claim, with a grade of the tail sluices of 1/35 to
1/36 the quantity moved was estimated at 2.4 yards per inch. The
material was coarse cemented gravel which required the use of powder.
At Cherokee Flat, with generally very fine material, high banks, head of 300 to 350 feet, and grade 1/32, 5.5 cubic yards are reported by the superintendent as the duty of the inch.
* See also Report State Engineer, 1880, part in. p. 24.
