xx Contents 



PAGES 



Rate at which Ground Water Surface Rises away from the 

 Drainage Outlet. In tile-drained field Where not 

 tile-drained 435, 436 



Depth at which Drains should ~be Placed. Kind of crop 

 Seasonal changes of ground water Character of soil 

 Distance between drains 436, 437 



Distance Between Drains. Texture of subsoil Depth of 

 drain Interval of time between rains or irrigations 

 Climatic conditions 437, 442 



Kinds of Drains. Closed Open Stone Wood Brick 



Peat Tile Cement 443-445 



How Water Enters Drains. Bate through the walls 

 Through the joints Care in making close joints Use 

 of collars 445, 446 



Fall or Gradient of Drains. Highest practicable Selecting 

 course for the main Care in laying to grade Change 

 of grade Use of silt well 447-449 



Size of Tile. No specific statement possible except where 

 all details are known Size increases with length 

 Seldom smaller than three inches in diameter Example 

 of sizes and lengths 449-452 



Outlet of Drains. Should have a clear fall Precautions 

 against injury from frost Connecting laterals with 

 mains 453 , 454 



Obstructions to Drains. From roots Kinds of trees most 



troublesome 455, 456 



Laying Out Systems of Tile 456-459 



Intercepting the Underflow from Hillsides 459, 460 



Draining Sinks and Ponds. By intercepting surface drain- 

 age By subdrainage 460-462 



The "Use of Trees in Drainage 4 r> 2, 463 



