300 Ground Water, Wells and Farm Drainage. 



1. Where single drains are laid here and there in irreg- 

 ular order to drain low places larger tile are required than 

 where a whole area is systematically treated, because in the 

 former cases a larger per cent, of surface water from sur- 

 rounding higher lands will flow upon the low areas under 

 which the drains are laid. 



2. The greater the fall the smaller the tile may be, 

 doubling the grade increasing the carrying -capacity nearly 

 one-third. 



FIG. 119a. Apparatus to demonstrate the Influence oi head, diameter, 

 length, and bends on the rate of discharge of water through lines of 

 tile and water pipe.. . 



3. The areas of cross section of tile increase with the 

 squares of their diameters: 



If their diameters are in the ratio of 2, 3, 4, 5, 6, 7, their 

 areas will be in the ratio of 4, 9, 16, 25, 36, 4-9, but as the 



