124 



LAND DRAINAGE AND IRRIGATION 



combination it is usually better to make the surface-run at one 

 side of the tile after the tile is laid and when the land is dried 

 sufficiently to permit horses to work (Fig. 59). When completed, 

 the surface-run carries the water during flood flow, while the tile 

 works throughout the year. 



Cult/voted 



. Tile combined with surface-run. The surface-run carries the water when there 

 is a flood, while the tile works throughout the year. (Wisconsin Station.) 



Tile Drainage is Profitable. (Figs. 60 and 61.) It costs from 

 twenty to forty-five dollars an acre for complete tiling, but the 

 benefits to be derived far exceed the cost, as is shown by the four 

 typical examples in the following table: 



Cost and Benefits of Tile Drainage 



Vertical Drains. Some vertical drains consist of openings or 

 cracks in underlying bed-rock, and cracks or openings made in 

 hard-pan 4 by the use of dynamite. It sometimes happens that a 



4 A hard and impervious substratum is commonly called a hard-pan. 

 It may vary in thickness from a few inches to three feet and more. 



