Field-Labourers 87 



saw, axe, and cart, all in one, and as the little creature 

 grows old her teeth are gradually worn down by the 

 hard work they have done, just as a workman's tools are 

 worn. 



The number of these ants is simply enormous ; and, 

 besides enriching the ground by the quantity of leaves 

 with which they fill their storehouses, they also per- 

 forate it to a considerable depth. Some of their sub- 

 terranean galleries have been traced down fifteen feet, 

 and found to be still descending. Whatever the depth 

 may be, from it they bring up the soil with which they 

 build their mounds ; and in Brazil there are very large 

 deposits of earth which have been raised to the surface 

 entirely by the ants. 



Thus not only is fresh soil continually exposed to the 

 action of air and rain, but ways are opened by which 

 the same air and rain may penetrate to the underlying 

 rocks and carry on the decaying process, as described 

 in an earlier chapter. Nor must it be forgotten that 

 wherever there is decaying vegetable matter, there 

 carbon-dioxide and other gases are formed, which are 

 absorbed by the rain in its passage through the earth, 

 and increase in a very high degree its power of acting 

 upon the rocks beneath. 



The ants' store-rooms, the worms' burrows with 

 their quantity of decaying leaves, the ground-squirrel's 

 hoards, and the beds made for themselves or their 

 young by mole, marmot, and the like, all increase the 

 organic matter and the supply of carbon-dioxide in the 

 soil ; while their various burrows, large and small, 

 make an easier passage for the rain. 



We cannot attempt to give more than a sketch, and 



