DRAINAGE INDICATIONS 195 



operations are simple. The chief precaution is to set the 

 tile at a good depth, remembering that muck soils lose 

 greatly in volume when drained, with the result that after 

 a few years the surface settles so near the tile that they 

 may be endangered from frost and agricultural tools. The 

 writer has been under the necessity of lowering a number 

 of systems of tile in muck soils because of the shrinking 

 of the mass and consequent settling of the surface. 



256. Small muck areas without natural outlets. It 

 frequently happens, especially in the glacial drift areas, 

 that one to several small muck areas occur on a single 



FIG. 89. To illustrate the isolated muck areas mentioned in paragraph 

 256. The line of tile laid to drain the area is shown. S, soil ; M , 

 muck ; /, underlying clay. 



farm. They may range from one-fourth acre to five 

 acres, entirely surrounded by higher land. When the 

 surface of the muck area stands higher than an adjacent 

 low area, as it often does, and when the horizontal dis- 

 tance between the two is not great, it may be drained 

 by laying a line of tile through the high ground, separat- 

 ing it from the adjacent low area, to the low ground. 

 This line may discharge into a line of tile in the lower 

 area (see Fig. 89) or into a natural water way or open 

 ditch. 



When the surface of the area is so low that sufficient 

 fall cannot be secured in draining to an adjacent area, 

 or where the horizontal distance is great or the separating 

 ridge is high, but one possible economical means of drain- 



