232 



GEOLOGY AND CHEMISTRY OF SOILS. 



of rock, over which the stream passes. The water suspends 

 large quantities of matter, which, in connection with the 

 mineral ingredients, is composed of various vegetable sub- 

 stances. This is deposited at the mouths of rivers, or, when 

 they overflow their banks, along their margins. This soil 

 will be fertile or barren according to the character of the 

 rock over which the rivers flow. Alluvial soil is generally the 

 most fertile and desirable of all soils. It appears to owe its 

 fertility to the fine state of its particles, or to its tex- 

 ture, and the condition of its vegetable constituents. For it 

 is found, by analysis, to contain less of vegetable food than 

 most other soils. But when rivers pass over sandstones, it 

 often happens, that no vegetable matter is intermingled, and 

 instead of fertility, nothing being washed down but silicious 

 matter, we have heaps of barren sand. Most of the alluvial 

 soils of New England and of the Western States are fertile ; 

 while many along the coast of the Southern States are bar- 

 ren plains. 



The value of alluvial soil depends upon another circum- 

 stance. If the sub-soil is gravelly or sandy, the water, and 

 with it, the manure passes down below the soil into the sub- 

 soil. This kind of soil is the most easily recognized of any ; 

 and every farmer knows it, under the name of interval or 

 meadow land. Its position also points it out, as it is gen- 

 erally found along the banks of rivers, and at their mouths. 

 In the latter case, the ocean waves often throw it back mix- 

 ed with marine exuvia upon the land, and form salt-marsh al- 

 luvions. The valley of the Connecticut river in New Eng- 

 land, presents some fine examples of river alluvium ; for ex- 

 ample, the meadows of Deerfield, Hadley, Northampton, etc. 

 But alluvial soils are much more extensive in the Middle and 

 Western States, especially in the vallies of the Mohawk, 

 Ohio, Mississippi and Missouri. In the West, it has receiv- 

 ed the name of bottom land. 



2. Peat alluvial soils. Among the alluvial soils n)ay be 



