GENERAL DRAINAGE INFORMATION 75 



on the size made and on the local situation in labor and 

 materials for the two kinds of tile. 



" Only sound tile giving a true ring should be put in 

 the ground. The ends should be reasonably square and 

 smooth, so that a good joint can be made. This is most 

 important when laying tile in soil of a quicksand nature. 

 Here special precautions against clogging are necessary." 



110. How water enters the tile. There is only one 

 way, in the case of glazed tile, for water to enter and that, 

 of course, is by way of the joints. 



In the case of porous tile, in all but the heavier soils, 

 the greater part of the water enters by way of the joints ; 

 this is probably true even in the case of the heavy soils. 



In the Soils Laboratory of the Michigan Agricultural 

 College, very careful tests showed that in the case of 

 common 6-inch tile, laid 4 rods apart, the rate at which 

 water entered through the walls was 2 tons to the acre in 

 30 hours, while in the case of 4-inch tile, laid in the same 

 way, the rate was 1.55 tons in 30 hours. A 4-inch tile, 

 of apparently more porous type, laid in the same way, 

 permitted water to flow through the walls at the rate of 

 1.66 tons to the acre in 30 hours. 



In the case of most cement tile, as they are commonly 

 made, water passed through the walls with great readiness. 

 Cement tile was also used in the tests referred to above, 

 and water was found to enter through the wall of 4-inch 

 cement tile, laid in the same manner and under the same 

 conditions as the common tile, at the rate of 1224 tons to 

 the acre in 30 hours. This is equivalent to over 8.6 acre 

 inches in 24 hours. 1 The readiness with which water 

 passes through the walls of the cement tile, as ordinarily 



1 Special Bulletin 56, Mich. Agr. College Experiment Station, 

 p. 5. 



