TILE DRAINING. 369 



rain-fall), the first 1500 feet in length, whether it be a single 

 drain or several laterals, may be made of the smallest sized 

 tiles (1 inch). Beyond this amount and up to 5000 feet, 

 2-inch tiles will suffice. From 5000 to 10,000 feet use 3- 

 incli, and from 10,000 to 20,000 feet use 4r-inch. 



These sizes would not suffice for the immediate removal 

 of all the water of a very heavy rain-fall, but it is to be re- 

 membered that before the water can get to the tiles it must 

 filter slowly through four feet of soil, and could reach the 

 drain but slowly, were it ever so large. Then again, it is 

 not important that the water of a heavy rain be removed 

 within an hour of its falling ; it does no harm to have it 

 settle slowly away, so long as it really does settle away, and 

 does not stand to be evaporated from the surface, nor to 

 flow off over it ; and it is desirable that the drains should 

 occasionally run "more than full," so that a strong flow of 

 water may wash out any obstructions that may have accu- 

 mulated in them. 



The question should not be so muck how large a tile is 

 necessary to carry the water, as how large a tile will the 

 water (after Jieavy rains) he able to flush and keep clean. 



In the foregoing. I have simply stated rules and principles 

 which have been proven by long experience to be correct. 

 The evidences of their truth and reliability, and the argu- 

 ments on which they are founded, could not be set forth in 

 the limited space which has been allowed for the subject in 



this book. The object here is to set forth rules and to give 



16* 



