124 MEASUREMENT OF FLOWING WATER.
again that above the top, and varies from 4-1/2 inches to 12 inches above the centre of the aperture.
The
Smartsville inch is calculated from a discharge through a four-inch
orifice with a seven-inch board top ; that is to say, the head is seven
inches above the opening, or nine inches above the centre. The bottom
of the aperture is on a level with the bottom of the box, and the
board which regulates the pressure is a plank one inch thick and seven
inches deep. Thus an opening two hundred and fifty inches long and
four inches wide, with a pressure of seven inches above the top of the
orifice, will discharge 1000 Smartsville miner's inches. Each square
inch of the opening will discharge 1.76 cubic feet per minute, which
approximates the discharge per inch of a two-inch orifice through a
three-inch plank with a head of nine inches above the centre of the
opening, the said discharge being 1.78 cubic feet per minute. The
Smartsville miner's inch will discharge 2534.40 cubic feet in
twenty-four hours, though in that district the inch is reckoned for
eleven hours only.
Other Inches.—The
miner's inch of the Park Canal and Mining Company, in El Dorado County,
discharges 1.39* cubic feet of water per minute. The inch of the South
Yuba Canal Company is computed from a discharge through a two-inch
aperture, over a one and one-half inch plank, with a head of six inches
above the centre of the orifice.
At
the North Bloomfield, Milton, and La Grange mines the inch has been
calculated from a discharge through an opening fifty inches long and
two inches wide, through a three-inch plank (outer inch chamfered),
with the water seven inches above the centre of the opening.
Determination of the Inch; Experiments at Columbia Hill.—To determine the value of this miner's inch, a series of experiments was made at Columbia Hill,
* Estimated by J. J. Crawford, M.E.
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