96 Genet- al Notices. 



and the uniform fineness of its particles. This may be well observed in any 

 gravelly country ; where, although in a ploughed field a large proportion of 

 the soil consists of small stones, yet, in old pasture lands, not a single pebble 

 will be found within some inches of the surface. The author's attention was 

 called to this subject by Mr. Wedgwood of Maer Hall, in Staffordshire, who 

 showed him several fields, some of which, a few years before, had been covered 

 with lime, and others with burnt marl and cinders. These substances, in 

 every case, were now buried to the depth of some inches beneath the turf, 

 as was ascertained by a careful examination of the several fields ; and Mr. 

 Darwin stated that the appearance, in all cases, was as if the fragments had, 

 as the farmers beheve, worked themselves down. But it did not appear to 

 him at all possible, that either the powdered lime, or the fragments of burnt 

 marl and the pebbles, could sink through compact earth to some inches 

 beneath the surface. Nor is it probable that the decay of the grass, although 

 adding to the surface of 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 had so lately been strewed on the surface. 

 Mr. Darwin had also observed near towns, in apparently unploughed fields, 

 pieces of pottery and bones some inches below the surface. So, on the moun- 

 tains of Chili, he had been perplexed by marine elevated shells, covered by 

 earth, in situations where rain could not have washed it on them. 



The explanation which occurred to Mr. Wedgwood of these phenomena, Mr. 

 Darwin does not doubt to be the correct one ; namely, that the whole is due to 

 the digestive process by which the common earth-worm is supported. On care- 

 fully examining between the blades of grass in the fields where the observations 

 had been made, the author found that there was scarcely a space of 2 in. square 

 without a little heap of the cylindrical castings of worms. It is well known that 

 worms, in their excavations, swallow earthy matter, and, having separated the 

 serviceable portion, eject at the mouth of their burrows the remainder, in 

 little intestine-shaped heaps. Hence, the fine particles are brought to the sur- 

 face, and the cinders, burnt marl, or powdered lime, would, by degrees, be 

 undermined, and eventually become covered by what was previously the un- 

 derlying earth. In a field in which cinders had been spread only half a year 

 before, Mr. Darwin actually saw the castings of the worms heaped on the 

 smaller fragments. 



On the above hypothesis, the great advantage of old pasture land, which 

 farmers are always averse to break up, is explained; for the worms must 

 require a considerable length of time to prepare a thick stratum of mould, by 

 thoroughly mingling the original constituent parts of the soil, as well as the 

 manures added by man. The author observes, that the digestive process of 

 animals is a geological power of greater extent than might at first be imagined. 

 In recent coral formations, the quantity of stone converted into the most im- 

 palpable mud, by the excavations of boring shells, and of nereidous animals, 

 must be very great. Numerous large fish (of the genus <S'parus) likewise 

 subsist by browsing on the living branches of coral. Mr. Darwin believes 

 that large portions of the chalk of Europe has been produced from coral, by 

 the digestive action of marine animals, in the same manner as mould have been 

 prepared by the same process on disintegrated rock. {Atkencemn, Nov. 25. 

 1837.) 



In our opinion, the phenomenon of the lime sinking in the soil is accounted 

 for by the difference between the specific gravity of that earth, and the mixture 

 of earths and organised matter, of which soils are originally composed. We have 

 known a dressing of chalk laid on the surface of a meadow, so as to form a stra- 

 tum of, say one-twentieth of an inch in thickness. In a number of years after- 

 wards, the same stratum, of the same thickness, was found several inches below 

 the surface. This appearance is quite familiar to farmers who have been in 

 the habit of manuring old grass lands with chalk or lime ; with whom it is a 

 common saying, that lime and other dressings of earth sink into the soil, and 

 that dung rises to the surface. Both assertions are strictly true, and both 



