158 The Drainage of Fens and Low Lands. 



APPENDIX. 



TABLE I. 



Explanation of Terms used. 



The quantities throughout are expressed, unless otherwise specially- 

 mentioned, as given below : — 



The mean velocity of the current in feet per second. 



Quantity in cubic feet or tons ; a cubic foot of water being taken 

 as 62 "50 lb., and a ton 35 '84 cubic feet. 



Rate of discharge = cubic feet per second. 



Hydraulic mean depk = the product found by dividing the sectional 

 area of a channel by the perimeter or wetted contour, that is, 

 length of the sides and bottom in contact with the water. This is 

 sometimes termed the hydraulic radius. 



Fall = the rate of inclination in the surface oi the water in feet 

 per mile. 



Head = the difference in the level of the surface of the water at 

 the upper and lower side of the place of the discharge in feet; e,g, 

 in an engine drain the head or height which the pump has to lift the 

 water is the vertical distance between the level of the surface of the 

 water in the drain on the inside, and that of the channel on the out- 

 side, into which it is discharged. In a submerged sluice the head is 

 in the same way the difference of level in the surface of the water on 

 the inside and outside. 



W,E.P. Horse-power in water actually lifted and discharged. 



TABLE 11. 



Weights and Measures relating to Water. 



I gallon of water weighs 10 lb. 



I „ seawater „ 10-20 „ 



I cubic foot of water „ (i2*'^2 



(generally taken as 62*50 lb.) 



I ton of water = 35-84 cubic feet 



do. do. =224 gallons. 



