Chap. Y. AND DENUDATION. 251 



I will now give such evidence of attrition 

 as I have been able to collect. In the 

 gizzards of some worms dug out of a thin bed 

 of mould over the chalk, there were many well- 

 rounded small fragments of chalk, and two 

 fragments of the shells of a land-mollusc (as 

 ascertained by their microscopical structure), 

 which latter were not only rounded but 

 somewhat polished. The calcareous concre- 

 tions formed in the calciferous glands, which 

 are often found in their gizzards, intestines, 

 and occasionally in their castings, when of 

 large size, sometimes appeared to have been 

 rounded; but with all calcareous bodies 

 the rounded appearance may be partly or 

 wholly due to their corrosion by carbonic 

 acid and the humus-acids. In the gizzards 

 of several worms collected in my kitchen 

 garden near a hothouse, eight little frag- 

 ments of cinders were found, and of these, 

 six appeared more or less rounded, as were 

 two bits of brick; but some other bits were 

 not at all rounded. A farm-road near 

 Abinger Hall had been covered seven years 

 before with brick-rubbish to the depth of 

 about 6 inches; turf had grown over this 

 12 



