366 STATE HORTICULTURAL SOCIETY. 



the proportion between the two being determined by the nature of the^ 

 rock from which it is derived, the length of time and character of the 

 atmospheric agencies working upon it, and the velocity of the water 

 rolling and pushing it along. The great variety existing in all these 

 conditions produces, of course, a great variety of soils. In our own 

 State, the fine clay like material that covers so large an area of it be- 

 speaks a remote source north of the great lakes. The rocks from which 

 it is derived must have been largely feldspathic, as otherwise such vast 

 quantities of clay and clay-like earth as exist in the Mississippi valley 

 could not have been produced ; but all rocks containing feldspar, no 

 matter what their structure and origin, contain, besides what will 

 eventually be clay, potash and phosphoric acid, the two elements with- 

 out which no agriculture is possible. 



How vast the quantities of these substances in our soils are, will 

 appear further on ; but as both of them, as mentioned, are soluble, they 

 would be washed away by the rains and carried into the ocean if, in 

 the disintegration of the original rock, combinations of them did not 

 exist or were formed, that prevented this leaching process. These 

 combinations, while yielding up to the growing plants from year to 

 year a certain amount from their stores, thereby rendering continuous 

 growth possible, are yet in their totality preventive of waste, and retain 

 enough of these most valuable ingredients of a soil to preserve to it 

 a moderate degree of fertility for hundreds of years to come. 



Alteration. — Upon this soil of a purely mineral character plants 

 begin to grow: First, lichens and plants of simple structure and low 

 organization, which, in time, die and make room for others, leaving 

 behind their bodies. Then, as the soil becomes richer in carbonaceous 

 and organic matters, higher organized plants occupy it, passing through 

 the same phases of life as the former, and enriching it at an increased 

 rate by the greater number as well as the greater bulk of their bodies 

 that fall victims to organic law. Lastly, the highest type of plants 

 makes its appearance, preparing and leaving in the course of time the 

 soil in the condition of virgin fertility in which our forefathers found 

 it, and of which, through ignorance of the laws of vegetable growth, 

 they'speedily despoiled it. 



But the bodies of plants, becoming incorporated in the soil, are 

 not the only causes of alterations which it undergoes by their growth. 

 Many other factors are active in changing a purely mineral to a fertile 

 agricultural soil. The roots penetrate it in all directions, and often to 

 a great depth, leaviRg after the death of the plant a network of narow 

 channels, through which air and water with their concomitant actions, 

 aided by heat and tirost, work a change in the character of the soil 



