Funna r ton of Soil. 



67 



same thing as plowing except that its influence extends 

 much deeper. 



Both earthworms and ants often burrow in the ground 

 to a depth of four feet, and in some cases more than nine, 

 bringing the material to the surface and forming passage- 

 ways down which the rains may wash the finer surface 

 soil. Fig. 22 shows a single pile of earth cast up by an 

 earthworm in the Botanic Gardens of Calcutta, and Fig. 23 

 shows the work of our common earthworm during a single 

 night in bringing up soil after a rain. 



FIG. 21. Section of vegetable mould in a field drained and reclaimed 15 years 

 before; showing turf, vegetable moulds without stones, mould with frag- 

 monts of burnt marl, coal cinders and quartz pebbles buried under the 

 iufluence of earthworms. One- third natural size. (After Darwin.) 



This frequent bringing of earth to the surface tends 

 to bury objects and gradually to lower them into the ground, 

 and Fig. 24 represents the results of one of Darwin's 

 studies, showing the amount of soil which has accumu 



