THE WHITE ANT : A THEORY. 



737 



denudation. There is the air which, with its carbonic acid and oxy- 

 gen, dissolves and decomposes the stubborn hills, and manufactures 

 out of them the softest soils of the valley. And there are the humic 

 acids, generated through decay, which filter through the ground and 

 manure and enrich the new-made soils. 



But this is not all, nor is this enough ; to prepare a surface film, 

 however rich, and to manure the soil beneath, will secure one crop, but 

 not a succession of crops. There must be a mixture and transference 

 of these layers, and a continued mixture and transference kept up from 

 age to age. The lower layer of soil, exhausted with bringing forth, 

 must be transferred to the top for change of air, and there it must lie 

 for a long time, increasing its substance, and recruiting its strength 

 among the invigorating elements. The upper film, restored, disinte- 

 grated, saturated with fertility and strength, must next be slowly low- 

 ered down again to where the rootlets are lying in wait for it, deep in 

 the under soil. 



Now, how is this last change brought about ? Man turns up the 

 crust with the plow, throwing up the exhausted earth, down the 

 refreshed soil, with infinite toil and patience. And Nature does it by 

 natural plowmen who, with equal industry, are busy all over the 

 world reversing the earth's crust, turning it over and over from year 

 to year, only much more slowly and much more thoroughly spadeful 

 by spadeful, foot by foot, and even grain by grain. Before x\dam 

 delved the garden of Eden these natural agriculturists were at work, 

 millions and millions of them in every part of the globe, at different 

 seasons and in different ways, tilling the world's fields. 



"standing out against the sky like obelisks." 



According to Mr. Darwin, the animal which performs this most 

 important function in nature is the earth-worm. The marvelous series 

 of observations by which the great naturalist substantiated his con- 

 clusion are too well known for repetition. Mr. Darwin calculates that 

 on every acre of land in England more than ten tons of dry earth are 

 passed through the bodies of worms and brought to the surface every 

 year : and he assures us that the whole soil of the country must pass 

 and repass through their bodies every few years. Some of this earth 

 is brought up from a considerable depth beneath the soil, for in order 

 to make its subterranean burrow the animal is compelled to swallow a 

 vol. xxvu. 47 



