CHAP. II The Web of Life 23 



feet of land chosen at random, Mr. Alvan Miilson collected 

 the worm-casts of a season and found that they weighed 

 when dry io| lbs. At this rate about 62,233 tons of sub- 

 soil would be brought in a year to the surface of each 

 square mile, and it is also calculated that every particle of 

 earth to the depth of two feet is brought to the surface once 

 in 27 years. We do not wonder that the district is fertile 

 and healthy. 



Devouring the earth as they make their holes, which are 

 often 4 or even 6 feet deep ; bruising the particles in their 

 gizzards, and thus liberating the minute elements of the soil ; 

 burying leaves and devouring them at leisure ; preparing the 

 way by their burrowing for plant roots and rain-drops, and 

 gradually covering the surface with their castings, worms have, 

 in the history of the habitable earth, been most important 

 factors in progress. Ploughers before the plough, they 

 have made the earth fruitful. It is fair, however, to 

 acknowledge that vegetable mould sometimes forms inde- 

 pendently of earthworms, that some other animals which 

 burrow or which devour dead plants must also help in the 

 process, and that the constant rain of atmospheric dust, as 

 Richthofen has especially noted, must not be overlooked. 



In 1777, Gilbert White wrote thus of the earthworms — 



"The most insignificant insects and reptiles are of much more 

 consequence and have much more influence in the economy of 

 nature than the incurious are aware of. . . . Earthworms, though in 

 appearance a small and despicable link in the chain of Nature, yet, 

 if lost, would make a lamentable chasm. . . . Worms seem to be 

 the great promoters of vegetation, which would proceed but lamely 

 without them, by boring, perforating, and loosening the soil, and 

 rendering it pervious to rains and the fibres of plants ; by drawing 

 straws and stalks of leaves and twigs into it ; and, most of all, by 

 throwing up such infinite numbers of lumps of earth called worm- 

 casts, which, being their excrement, is a fine manure for grain and 

 grass. Worms probably provide new soil for hills and slopes where 

 the rain washes the earth away ; and they affect slopes probably to 

 avoid being flooded. . . . The earth without worms would soon 

 become cold, hard-bound, and void of fermentation, and con- 

 sequently sterile. . . . These hints we think proper to throw out, in 

 order to set the inquisitive and discerning to work. A good mono- 



