TILE DRAINAGE 21 



first manufacturing' plant was established here in 1838. 

 The use of drain tile was not common until about 1850, 

 and only a comparatively few Avere used until after the 

 Civil War. At the present time there are over 5,000 fac- 

 tories at work in the United States with an annual output 

 valued at $3,200,000. 



EFFECTS OF TILE DRAINAGE. 



The first and one of the most obvious effects of drainage 

 is to rid the soil of its surplus water. Plants require a 

 moist soil but they cannot grow in a wet one. The water 

 w^hich makes a soil moist is that which adheres to the indi- 

 vidual soil particles in the shape of a thin film and which 

 completely fills only the smaller spaces between the par- 

 ticles. This kind of soil water is called capillary because 

 it will move through the soil in any direction by what 

 is known as capillary attraction. It is believed that plants 

 must depend entirely upon this kind of water for their 

 supply, and hence its maintenance is of the greatest im- 

 portance. On the other hand, the water which makes a 

 soil wet fills all the spaces in the soil which are not occu- 

 pied by the soil particles themselves. This kind of water 

 is called gravitational because it can move in only one 

 direction and that is downwards, through the force of 

 gravity. Plants cannot grow until this surplus gravita- 

 tional water has been removed. The ''freezing out" or 

 heaving of winter grain and posts on clay soils is not oc- 

 casioned by the low temperature but by the formation of 

 ice in the upper part of the soil, which causes an expansion 

 and a consequent upward movement in the direction of 

 least resistance. If the soil is drained the water will pass 

 off and the injury and trouble on account of freezing will 

 be largely avoided. 



Soils are better ventilated by drainage. The roots of 

 plants require air just as do the parts above ground. 

 When nearly all the spaces in the soil are filled with water, 

 very little air can exist there. When we remember, too. 



