AGRICULTURAL ENGI:N^EERING. 177 



A miner's inch is theoretically such a quantity of water as 

 will flow through an aperture i inch square in a board 2 

 inches thick under a head of water of 6 inches in one sec- 

 ond of time, and it is equal to 0.194 gallon, or 0.C259337 

 cubic foot, per second, or to 11.64 gal., or i.556o24cubic ft., 

 per minute. The amount of water flowing through a given 

 aperture in a given time varies, however, with the head ot 

 water over the opening, and also with the form of the 

 opening. In Colorado the miner's inch legalized by statute 

 equals 11. 7 gal. per min. The California miner's inch, how- 

 ever, equals only 9 gal. per min., 100 Colorado inches being, 

 accordingly, equal to 130 California inches. One hundred 

 Colorado inches will cover an acre to a depth of 5.2 ft. in 

 24 hours ; 100 California inches will cover the same area 

 only to a depth of 4 ft. in the same time. Fifty California 

 inches are, therefore, approximately equal to i second- 

 foot, and 50 Colorado inches equal to about three tenths 

 more. 



An acre-'foot of water is the amount required to cover an 

 acre of ground to a depth of i foot. This is 43,560 cubic 

 feet, or 325,851.45 gal. Its weight is 1213 tons 2113 pounds, 

 at 2240 pounds to the ton. 



The amount of water required to cover an acre of ground 

 to a depth of i inch is 3630 cubic feet, or 27,154.29 gal. Its 

 weight is loi tons 362! pounds, at 2240 pounds to the 

 ton. 



A second-foot is the most satisfactory because the most 

 definite unit of measurement for flowing water. It is used 

 by the U. S. Government in the gauging of rivers and 

 streams, and is rapidly superseding the miner's inch in the 

 measurement of water for irrigation. It is the quantity rep- 

 resented by a stream i foot wide and i foot deep flowing 

 at the average rate of i foot per second. In other words, 

 it is I cub. ft. per second, 60 cub. ft. per min., 3600 cub. 

 ft. per hour, etc. A stream flowing continuously at the 

 average rate of i second-foot would carry in one day of 24 

 hours 86,400 cub. ft., or 646,316.9 gal., sufficient to cover 

 i||y acres to a depth of i ft. Flowing continuously for one 

 year of 365 days, such a stream would carry 31,536,000 cub. 



