DISINTEGRATING WORK OF ANIMALS. 451 



Marsh," Shaler, 6 Merrill, c and others have strongly emphasized the 

 ravages upon the soil as the result of man's work. They show how even 

 from man's point of view the present careless methods of cultivation will in 

 the future work to his disaster. However, for the present purpose I wish 

 to emphasize the fact that as the soil is transported to the streams and to 

 the ocean new material is exposed to the forces of disintegration and decom- 

 position, and thus the process of weathering is accelerated far bevond the 

 speed under natural conditions. 



General statements. — In conclusion, we see that the animals, from the earth- 

 worm, ant, and termite to the larger burrowing animals, throughout all parts 

 of the earth which are thickly inhabited by animals, are constantly working 

 over the soil to a considerable depth. By the work of these animals there 

 is a constant migration or movement of material from the soil or subsoil to 

 the surface, where the material is directly exposed to all the weathering 

 agencies. Man has denuded a large part of the surface of the earth of its 

 protecting vegetation. Thus, as a consequence of the work of all the 

 animals, the soil is more read)' to be caught up by running water and trans- 

 ported to the streams. This has other far-reaching consequences in furnish- 

 ing increased amounts of sediments and salts to the sea, and consequently 

 greatly accelerating the speed of upbuilding of the sedimentary rocks. 

 Hence animals perform a very important mechanical function in weathering 

 the rocks, in promoting- their transportation, and in exposing new surfaces 

 to the weathering forces ; and consequently they greatly accelerate denuda- 

 tion and deposition. 



CHEMICAL WORK. 



Chemical work is accomplished by all the agents of metamorphism, 

 viz, (1) plants, (2) animals, (3) water solutions, and (4) gaseous solutions. 

 These agents will first be considered and then their joint work. 



« Marsh, George P., Man and nature, or physical geography as modified by human action, Chas. 

 Scribner & Co, New York, 1869, pp. 576-577. 



»Shaler, N. S., The origin and nature of soils: Twelfth Ann. Rept. U. S. Geol. Survey, pt. 1, 1891, 

 pp. 329-339. 



(•Merrill, George P., Rocks, rock-weathering, and soils, Macmillan Co., New York, 1897, pp. 

 396-398. 



