The Soil 11 



the northern part of the continent transported rocks 

 totally dijfferent from the fast rocks of the neighborhood. 

 With the deposit of the earthy matter which the glaciers 

 had prepared and the restoring warmth of the cHmate, 

 vegetation again started northward, and through its 

 growth and decay contributed to the formation of what 

 we to-day know as soil, in distinction from the original 

 clay we call subsoil. But the action of the elements still 

 continued to disintegrate the rocks and to transport the 

 particles to lower levels. The limestone was formed 

 from the lime washed into the lakes and from the remains 

 of shellfish and vegetable decay, until by degrees the lake 

 was filled and the deep soil of the Hmestone valleys was 

 deposited. This soil, not being formed from the disin- 

 tegration of the rock below, is often more deficient in lime 

 than soils that are formed from the decay of the rocks on 

 which they rest; hence it is often found that soils nomi- 

 nally limestone need applications of lime in cultivation 

 more than some soils on a very different rock formation. 

 Through all the long ages the work of the 

 Land water has gone on. The rivers, which were 



Formations jj^mense floods following the glacial age, 

 by Rivers , , , . , ° . j • j 



and Rains gradually shrunk m volume as they dramed 



away the great accumulation of water. The 

 result is seen to-day in all the river valleys where the 

 different heights of the water are shown by the terraces 

 back from the present river bottom lands commonly 

 known as second and third bottoms. But the soil is still 

 being continually washed from the mountains and hills, 

 and the formation of bottom soils along the river is con- 

 tinually going on with every overflow. Great rivers, like 



