575 



lying on the surface, or entangled in the roots of the grass. The 

 second field examined was remarkable only from the cinders being 

 now buried in a layer, nearly an inch thick, three inches beneath the 

 surface. This layer was in parts so continuous, that the superficial 

 mould was only attached to the subsoil of red clay by the longer 

 roots of the grass. 



The history of the third field is more complete. Previously to fif- 

 teen years since, it was waste land ; but at that time it was drained, 

 harrowed, ploughed, and well covered with burnt marl and cinders. It 

 has not since been disturbed, and now supports a tolerably good pasture. 

 The section here was, turf half an inch, mould two inches and a half, 

 a layer one and a half inch thick, composed of fragments of burnt marl 

 (conspicuous from theirbright redcolour,and some of considerable size, 

 namely, one inch by half an inch broad, and a quarter thick), of cinders, 

 and a few quartz pebbles mingled with earth; lastly, about four inches 

 and a half beneath the surface was the original, black, peaty soil. 

 Thus beneath a layer (nearly four inches thick) of fine particles of 

 earth, mixed with some vegetable matter, those substances now oc- 

 curred, which, fifteen years before, had been spread on the surface. 

 Mr. Darwin stated that the appearance in all cases was as if the frag- 

 ments had, as the farmers believe, worked themselves down. It does 

 not, however, appear at all possible, that either the powdered lime or 

 the fragments of burnt marl and the pebbles could sink through com- 

 pact earth to some inches beneath the surface, and still remain in a 

 continuous layer. Nor is it probable that the decay of the grass, al- 

 though adding to the surface some of the constituent parts of the 

 mould, should separate, in so short a time, the fine from the coarse 

 earth, and accumulate the former on those objects, which so lately 

 were strewed on the surface. Mr. Darwin also remarked, that 

 near towns, in fields which did not appear to have been ploughed, 

 he had often been surprised by finding pieces of pottery and bones 

 some inches below the turf. On the mountains of Chile he had been 

 perplexed by noticing elevated marine shells, covered by earth, in si- 

 tuations where rain could not have washed it on them. 



The explanation of these circumstances, which occurred to Mr. 

 Wedgwood, although it may at first appear trivial, the author does not 

 doubt is the correct one, namely, that the whole is due to the di- 

 gestive process, by which ihe common earth-worm is supported. On 

 carefully examining between the blades of grass in the fields above 

 described, the author found, that there was scarcely a space of 

 two inches square without a little heap of the cylindrical castings 

 of worms. It is well known that worms swallow earthy matter, and 

 that having separated the serviceable portion, they eject at the 

 mouth of their burrows, the remainder in little intestine-shaped 

 heaps. The worm is unable to swallow coarse particles, and as it 

 would naturally avoid pure lime, the fine earth lying beneath 

 either the cinders and burnt marl, or the powdered lime, would, by a 

 slow process, be removed, and thrown up to the surface. This sup- 

 position is not imaginary, for in the field in which cinders had been 

 spread out only half a year before, Mr. Darwin actually saw the cast- 

 ings of the worms heaped on the smaller fragments. Nor is the 



