694 PRINCIPLES OF STRATIGRAPHY 



mounds are sometimes 14 feet high (4^ meters), and from 10 to 

 30 feet (3 to 9 meters) in basal diameter. They are often so close 

 together that their bases touch each other. Branner has estimated 

 (3:^69) that in an area of 10,000 square meters on which 53 

 mounds occurred the amount of earth brought up by ants and built 

 into mounds would cover the area with a layer 22.25 centimeters in 

 thickness. 



The termites' nests rise to 31^^ meters in height, and may be 3 

 meters in basal diameter. They, too, are often closely set, those 

 along the upper Paraguay being not over 3 meters apart. (Fig. 



I33-) 



A comparison of the work of earthworms and ants gave the 

 following result (Branner-3 : ^pj). Total weight of earth brought 

 to the surface in 100 years over i hectare (10,000 square meters) : 



By worms in England (Darwin-4), 2,598,500 kilograms. 



By ants in Brazil (Branner-3), 3,226,250 kilograms. 



The work of ants on the soil and subsoil is summarized by 

 Branner as follows (3:^9^) : 



Directly : 



1. "By their habits of making underground excavations that 

 radiate from a central nucleus and often aggregate several miles 

 in length. 



2. "By opening the soil to the atmospheric air and gases. 



3. "By bringing to the surface large quantities of soil and sub- 

 soil. 



4. "By introducing into their subterranean excavations large 

 quantities of organic matter, which must yield acids that afifect the 

 soil and the subjacent rocks. 



5. "By using these excavations for habitations and the pro- 

 duction of gases that attack the soil and its contained minerals." 



Indirectly. 



6. "By the periodic passage and circulation of meteoric waters 

 through their extensive tunnels. 



7. "By affecting the availability of the soil for agricultural 

 purposes. 



8. "By affecting the habitability of the land by man. 



9. "By the destruction of crops. 



10. "By the consumption (by the termites) of dead plants and 

 of timbers and lumber used in houses and for the manufacture of 

 furniture, machinery, etc." 



In temperate regions ants are less active, though, according to 

 Shaler, they transfer annually half a centimeter of material from 

 the subsoil to the surface, in certain fields in Massachusetts. (8.) 



