1 8 ENGINEERING FOR LAND DRAINAGE. 



erly cultivated. In some instances a layer of gumbo 

 is found beneath a fine bed of loam, and supports it as 

 a subsoil. 



Muck is a black soil composed largely of vegetable 

 matter and is found in swamps. It frequently requires 

 exposure to the atmosphere for a time before it can be 

 treated as a workable soil. 



Peat is partially decayed swamp turf which when 

 dry will burn readily. The underlying bed is usually 

 muck or blue-black clay. 



Hard'pa7i is the name applied to a tough, impene- 

 trable layer underlying a fairly fertile soil. A hard- 

 pan proper is made up of soil particles which are being 

 cemented together again by the solutions of lime, iron, 

 or silicates that descend through the soil. Commonly 

 speaking, however, any hard clay subsoil is termed 

 hard-pan. 



Each Soil an Individual. 



Each soil possesses a composition and character of 

 its own, and it follows that its capabilities, require- 

 ments, and treatment should be taken up individually. 

 Soil investigations are necessarily experimental, be 

 they made with reference to productive capabilities, 

 drainage properties or irrigation possibilities. Each 

 case should be taken up by itself and studied with 

 special reference to its character and condition. When 

 plants are chemically analyzed they are found to con- 

 tain elements found in the soil with the exception 

 of aluminum- However, the element which appears 

 most abundant in the plant is frequently found in the 

 most meager quantities in the soil which produces it, 



