The Soil 19 



53*767, and from their average weight this would mean 

 356 pounds of worms in an acre of land. The weight of 

 single worm castings was found to be over two ounces as 

 an average. This shows well the great amount that can 

 be brought from the subsoil to the surface by this appar- 

 ently insignificant means. 



Thus we see that numerous agencies have 

 Summary of ^^^^ ^^ ^^^^ -^^ ^^v^ formation of the soils 

 Nature's 



Processes ^^ cultivate. The rain water, with its car- 



bonic acid, disintegrated the rocks; the 

 frost helped, and the water transported the fine materials. 

 The glaciers ground the rocks through unnumbered ages, 

 and their melting carried the muddy flood over all the 

 earth. The growth and decay of vegetation added fer- 

 tihty to it with the materials the trees had gotten from the 

 air; for you will remember that over 97 per cent, of their 

 structure comes from the air and is thus returned to the 

 soil in their decay. Then in some cases the coral polyp 

 has extended the land seaward and enabled the vege- 

 table soil to accumulate, and the Uttle earthworm has 

 industriously burrowed in this soil and deepened the 

 surface soil with material brought from below. Lime- 

 stone deposits have been heaved up from the bottom 

 of the sea. The rivers have transported soil from place 

 to place, and shrinking left the river flats or bottoms 

 elevated for cultivation. 



Even in our own days we can see how 

 Wasted^loU mature restores a wasted soil. Men culti- 

 vate a field carelessly in a single crop till 

 they say it is worn out. This has been done particularly 

 in the Southern cotton and tobacco sections. The field is 



