miner’s inch

In the western United States and Canada, and in New Zealand, late 19ᵗʰ – early 20ᵗʰ century, a unit of stream flow used by miners. The size of the unit varied greatly from place to place.

Locale Volume
cubic feet of water
per minute
New Zealand 60 Elwyn E. Seelye.
Data Book for Civil Engineers. Vol. 2. Specifications and Costs.
New York: John Wiley, 1951.
British Columbia 1.68 Alfred H. Ricketts.
American Mining Law with Forms and Precedents. 4th ed. enlarged and revised.
California Division of Mines Bulletin 123,  Feb. 1943.
Colorado 1.56
California (act of the California legislature
 of May 23, 1901),
Montana, Oregon
southern California (“regardless of the legal definition”),
Idaho, Nebraska, Nevada, New Mexico,
North Dakota, South Dakota, Utah

A miner' inch day was the quantity of water produced by a flow of 1 miner's inch for a period of one day.



1″ square aperture through a 2″ plank with water 6″ above the top of the aperture, 2,274 cubic feet in 24 hours,

[ which does not agree with Fay's definition of the miner's inch as a flow of 1.5 cu. ft per minute, which would be 2160 cubic feet in 24 hours. -ed.]

... the miner's inch is a flow of 1.5 cubic feet per minute through any aperture or orifice.

Albert H. Fay.
A Glossary of the Mining and Mineral Industries.
U.S. Bureau of Mines Bulletin 95, Washington, 1918.


The term Miner's Inch is more or less indefinite, for the reason that California water companies do not all use the same head above the centre of the aperture, and the inch varies from 1.36 to 1.73 cu. ft. per min., but the most common measurement is through an aperture 2 ins. high and whatever length is required, and through a plank 1¼ inches thick. The lower edge of the aperture should be 2 ins. above the bottom of the measuring-box, and the plank 5 ins. high above the aperture, thus making a 6 in. head above the centre of the stream. Each square inch of this opening represents a miner's inch, which is equal to a flow of 1½ cu. ft. per min.

William Kent.
The Mechanical Engineers' Pocket-Book. 9th edition.
New York: John Wiley & Sons, 1916.
Page 18.


1 second-foot equals 40 California miner's inches. (Law of March 23, 1901.)
1 second-foot equals 38.4 Colorado miner's inches.
1 second-foot equals 7.48 United States gallons per second; equals 448.8 gallons per minute; equals 646 317 gallons per day.
1 second-foot equals about one acre-inch per hour.
1 second-foot falling 10 feet equals 1.136 horse-power.
100 California miner's inches equal 18.7 United States gallons per second.
100 California miner's inches equal 96.0 Colorado miner's inches.
100 California miner's inches for one day equal 4.96 acre-feet.
100 Colorado miner's inches equal 2.60 second-feet.
100 Colorado miner's inches equal 19.5 United States gallons per second.
100 Colorado miner's inches equal 104 California miner's inches.
100 Colorado miner's inches for one day equal 5.17 acre-feet.

National Tube Company.
Book of Standards.
Pittsburgh: 1913.
Page 312.


Commentary on the unit from a late 19ᵗʰ century author, and a drawing of the device often used, is provided here.

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