76 LAND DRAINAGE 



made, may be easily observed if one will hold a tile so that 

 one can see along the inner surface and then slowly pour 

 water upon the upper outer surface. It requires but a 

 few seconds for the water to pass through and hang in 

 large drops on the inside of the tile. In heavy soils, a 

 tile possessing the porosity of the cement is greatly to be 

 desired. Undoubtedly Elliott would disapprove of the 

 use of cement tile of so open structure. 



111. Tile systems. In the draining of a piece of land, 

 there are several things that should be carefully considered. 

 It may be that a single line of tile will be sufficient to re- 

 move the surplus water from the area to be drained. This 

 is likely to be the case if the area is not over 100 to 150 

 feet wide, provided the soil is relatively open. If the 

 width is greater than 150 feet, or if it is as little as 100 

 feet, with a relatively impervious soil, it is probable that 

 more than one line of tile will be required. If the one line 

 is not sufficient, then a system should be introduced, the 

 style of which will depend upon the surface and shape of 

 the area and, possibly, on the notion of the one who is 

 installing the system. 



Two general systems employed in tile drainage are illus- 

 trated in Figs. 24, 25, 26. All kinds of combinations of 

 these are found in actual practice. (See Figs. 27, 28, and 

 29.) In any system of tile, that line which receives the 

 water from all the other parts of the system is called the 

 main, and all the lines receiving the water directly from the 

 soil and conveying it to a main are called laterals. If 

 there should be more than one system of laterals, each 

 system flowing into another line than the main, which in 

 turn carries the water to the main, each of these lines 

 is called a sub-main. Figures 27 and 28 illustrate this 

 point. 



