26 TILE DKAINAGE 



There is a close relation between the depth and distance 

 apart of drains. The distance apart will depend upon the 

 depth. From Figure 1 it will be seen in order to keep the 

 ground water lowered a certain distance below the surface 

 between lines of tile that the deeper the tile are placed, 

 the further they may be apart. The distance apart is also 

 dependent upon the texture of the soil through which the 

 water has to filter. In a close textured soil, composed of 

 very fine particles, such as our clay soils are, the resistance 

 to the flow is very great, and as a result the ground water 

 surface will have a steeper slope and will rise rapidly back 

 from the drain. Here, then, unless the lines of tile are 

 placed near- together or else at a good depth, the ground 

 water will come clear to the surface or very near it, and 

 the drains will not be doing efficient work. This matter 

 is also illustrated in Figure 1. As before noted, tiles 

 should not be placed deep in a fine clay soil, so the only 

 remaining thing to do is to place them in lines close to- 

 gether. Concerning some lines of tile which were laid 

 about sixty feet apart in a heavy clay soil here on the 

 Station farm several years ago, it was noticed that about 

 midway between them no appreciable effects of the drains 

 could be seen, while for a distance of fifteen or twenty feet 

 on either side of them the ground was noticeably drier. 

 Practical experience and observation has shown that from 

 thirty to forty feet is the proper distance for thorough 

 drainage in clay soils. In more open and porous soils, 

 which will admit of the tiles being placed deeper and at 

 the same time allow the water to filter more readily through 

 them, general field practice dictates a distance of fifty to 

 one hundred feet. 



LAYING OUT DRAINS. 



The first thing to do in laying out a system of drains is 

 to decide on the location of the outlet or outlets. This 

 should always be at the lowest available point, so as to 

 secure the greatest amount of fall. Just as few outlets 



