THE EARTHWORM. 21 



in these he found similar indications of a gradually 

 increasing thickness in the surface-soil, and beneath, 

 an accumulation of pebbles, cinders and lime, which 

 had originally been deposited on the surface. In one 

 field, for instance, the cinders which had been thrown 

 on the surface three years previously, were bui-ied to 

 the depth of an inch; in another they were buried 

 three inches deep, and formed a layer an inch in 

 thickness. But let us give the narrative in his own 

 words : — 



" The appearance in aU the above cases was as if 

 (in the language of farmers who are acquainted with 

 these facts) the fragments had • worked themselves 

 down.' It is, however, scarcely possible that ciaders 

 or pebbles, and still less powdered quicklime, could 

 sink through compact earth and a layer of matted 

 roots of vegetables, to a depth of some inches. The 

 explanation of these facts which occurred to Mr. 

 Wedgewood" (his host), "though it may appear trivial 

 at first, I have no doubt is the correct one, namely 

 that the whole operation is due to the digestive pro- 

 cess in the common Earthworm. On carefully exa- 

 mining between the blades of grass in the fields above 

 described, I found scarcely a space of two inches 

 square without a little heap of cylindrical castings of 

 worms. It is well known that worms in their exca- 

 vations swallow earthy matter, and that, having sepa- 

 rated the portion which serves for their nutriment, 

 they eject at the mouth of their burrows the remainder 

 in little intestine- shaped heaps. These partly retain 



