22 



ENGINEERING ON THE FARM 



Second-foot. The flow of a stream is indicated by the num- 

 ber of second-feet. A second-foot is i cubic foot of water 

 passing a given point in i second of time. For example, 

 a stream flowing 10 second-feet means that 10 cubic feet 

 of water pass a given point each second. 



Acre-foot. The acre-foot is a common term in irrigated 

 country and is also used by soil men. It means a depth of 

 i foot over an area of i acre and is equivalent to 43,560 cubic 

 feet or 325,851 gallons. For example, if it requires 3 acre- 

 feet of water to produce an acre of wheat, it is understood 

 to mean that sufficient water must be applied to that acre 

 of wheat so that if all the water were placed on it at one time 

 the water would be 3 feet deep over the acre. 



Wire gouge. The thickness of sheet metal and the diam- 

 eter of wire and other small iron or steel material such as 

 nails, screws, etc., are designated by a specific number which 

 is measured by a wire gauge (Fig. 5, page 21). Unfortunately 

 the wire gauges are not standardized, and in using the 

 gauge it is necessary to specify the gauge name, as thickness 

 indicated by one gauge varies from thickness indicated by 

 the corresponding number of another gauge. 



Table Showing a Comparison of Wire Gauges 

 in Decimals of an Inch 



No. 



OOOO 

 OOO. 

 OO. . 

 O. . . 

 I . . . 

 2. . . 



4... 



5... 



6. . . 



7 ... 

 8. . . 



No. 



19 

 20 



21 



22 



23 

 24 

 25 

 26 



27 

 28 



29 



30 



London 



,042 



035 



031 



.029 



.027 



.025 



.023 



020 



Ol8 



Ol6 



OI5 



OI3 



Birm- 

 ingham 

 Stubs 



.042 



•035 

 .032 



.028 

 .025 

 .022 

 .020 

 .Ol8 

 .Ol6 

 .014 

 .013 

 .OI2 



Brown 



& 

 Sharp's 

 Ameri- 

 can 



•035 

 .031 

 .028 

 .025 

 .022 

 .020 

 .017 



.015 

 .014 

 .012 

 .Oil 

 .OIO 



