Chap. V. AND DENUDATION. 261 



" hundred yards." * Nor should we forget, in 

 considering the power which worms exert in 

 triturating particles of rock, that there is good 

 evidence that on each acre of land, which is 

 sufficiently damp and not too sandy, gravelly 

 or rocky for worms to inhabit, a weight of 

 more than ten tons of earth annually passes 

 through their bodies and is brought to the 

 surface. The result for a country of the size 

 of Great Britain, within a period not very 

 long in a geological sense, such as a million 

 years, cannot be insignificant ; for the ten tons 

 of earth has to be multiplied first by the above 

 number of years, and then by the number of 

 acres fully stocked with worms; and in 

 England, together with Scotland, the land 

 which is cultivated and is well fitted for these 

 animals, has been estimated at above 32 

 million acres. The product is 320 million 

 million tons of earth. 



* Anniversary Address : ' The Quarterly Journal of the 

 Geological Soc.' May 1880, p. 59. 



T 2 



