12 Practical Farming 



the Mississippi, carry clear to the sea vast amounts of soil 

 and gradually build up deltas, which are finally elevated 

 into cultivable lands. The Mississippi in times of flood 

 has cut new channels, leaving the old bends as lakes back 

 from the main current. The first effect of a change of 

 location of the land along the river is the formation of a 

 sand bar. On this vegetation grows, and finally a forest 

 of cottonwoods, and above the sand a deep layer of vege- 

 table soil is formed, often to be again undermined by a 

 freak of the current in flood time. In all low bottom 

 lands we commonly find that the water first drops the 

 sand; as the current abates the brick clay in its finely 

 comminuted state is deposited, and on this again the vege- 

 table remains for the cultivated soil. In warm climates 

 the formation of soil where lakes existed goes on rapidly 

 through the accumulation of vegetation. This gradually 

 fills the lake with its decay and deposits its component 

 parts, till finally the lake is soil of great fertihty, and the 

 vegetation may have made great mineral deposits from 

 the iron it contains. We find these immense deposits of 

 iron now being utilized in the ancient lake beds of Minne- 

 sota, while in the warmer chmate of California soils of 

 immense fertihty are thus made. 



Study the face of a rocky cHff and note 

 The Action what a great accumulation of broken and 

 hi Soil^ pulverized rock forms the sloping talus at 



Formation its base. All of this came from the action 

 of water and frost on the surface of the cHff, 

 which is constantly forcing off particles, and now and then 

 a big portion of rock. Then a river at the base of this cUff 

 rises and the finer particles are washed along with the cur- 



