42 



cases will have little experience in this kind of work, a steeper grade 

 will be much safer. With ordinary skill and care excellent work can 

 be done with grades ranging from 3 to 5 or 6 inches to each 100 feet. 

 Whatever the grade, much care should be taken to make it as uniform 

 as possible. 



The Size of Tile to lay. 



The amount of water carried by tile of any given size varies with the 

 grade. The area of the circle which measures the bore varies with the 

 square of the diameter. It may appear, therefore, that at a uniform 

 grade the aiDpHcation of this rule will indicate the relative capacity of 

 different sizes to carry water. Thus, for example, it might be supposed 

 that the 3-inch tile would carry two and one-quarter times as much 

 water as the 2-inch tile because the square of 3 is 9, and 9 is two and 

 one-quarter times 4, which is the square of 2. As a matter of fact, the 

 3-inch tile will carry more than two and one-quarter times as much 

 water as the 2-inch, because the amount of friction is relatively greater 

 in the smaller sizes. Friction being taken into account, tiles of different 

 sizes, according to Wheeler,' have about the following relative capacity 

 to carry water, as compared with 2-inch tile taken as a basis of com- 

 parison : — 



2^-inch tile 1.5 times the water carried by 2-inch tile. 



3 -inch tile 2.5 times the water carried by 2-inch tile. 



4 -inch tile 5.0 times the water carried by 2-inch tile. 



5 -inch tile 7 . 5 times the water carried by 2-inch tile. 



6 -inch tile 12.5 times the water carried by 2-inch tile. 

 8 -inch tile 25.0 times the water carried by 2-inch tile. 



(a) Size for Laterals. — Throughout the eastern States 2-inch tile 

 is most commonly used for laterals, but in the middle and western 

 States larger tiles are usually employed. Chamberlain says : — 



The tendency toward larger size, especially in the rather level prairies of the 

 west, is manifest and wise. The soil is more porous, and hence laterals may be 

 much farther apart, and wisely laid deeper (even 4 or 4^ feet), than in our more 

 compact, clayey soils in Ohio. Also, as the grades there are less, the sizes must 

 be larger. ... In Illinois 3 and 4 inch tiles are now the smallest sizes found 

 at most tile kilns. The material is not expensive, and the tendency toward 

 large sizes is wise, except where freights or long hauling make the weight im- 

 portant. 



(6) Size needed for Mains. — Chamberlain has given rules for the 

 size of mains in tile drainage which appear to be worth stating. Ac- 

 cording to his rule, to determine the number of acres that can be 

 drained by tiles of different sizes when the grade is not more than 3 

 inches in 100 feet: square the diameter of the tile and cUvide the result 

 by 4. It will be found that the areas drained by different sized mains 

 according to this rule will be as follows : — 



3-inch tile, . . • 2J acres. | 5-inch tile, . . ■ 6^ acres. 



4-inch tile, . .4 acres. I 6-inch tile, . . .9 acres. 



1 Hints on Land Drainage, Agriculture of Massachusetts, 1895. 



