286 



APPENDIX. 



In order to make the above formula more intelligible: 

 Let L = 80 rods or 1320 feet. 

 " H = 50 feet. 

 " D = 2 inches. 

 '* Q = gallons. 



Then Q =0.608 V (32 x-,f|o) = 0-67; or, the same maybe thus ex- 

 pressed in Avords : 



Divide the height (50) by the length (1320) ; multiply the quotient by 

 the fifth power of the diameter (fifth power of 2"= 32); extract the 

 square root of the product, which, being multiplied by 0.60S, will give 

 (0.67) the number of gallons the tube will discharge in one second ; 

 which, in this case, is 40 gallons in one miuute. 



VELOCITY OF WATEPw IN TILE DRAINS. 



An acre of land in a Avet time contains about one thousand spare 

 hogsheads of water. An underdrain will carry off from a strip of land 

 about two rods wide, and one eighty rods long will drain an acre. The 

 following table will show the size of the tile required to drain an acre in 

 two days' time, (the longest admissible), at dififerent rates of descent, or 

 the size for any larger area : 



Diameter of Bore. Rate of Descent. 



2 inches. 1 foot in 100 



2 inches. 1 foot in 50 



2 inches. 1 foot in 20 



2 inches. 1 foot in 10 



3 inches. 1 foot in 100 

 3 inches. 1 foot in 50 

 3 inches. 1 foot in 20 



3 inches. 1 foot in 10 



4 inches. 1 foot in 100 

 4 inches. 1 foot in 50 

 4 inches. 1 foot in 20 

 4 inches. 1 foot in 10 



A deduction of one-third to one-half must be made for the roughness 

 of the tile or imperfection in laying. The drains must be of some 

 length, to give the water velocity, and these numbers do not, therefore, 

 apply to very short drains. 



