Geology of Cambridgeshire, 249 



and of all sizes, from a hazel nut to an ordinary potatoe. The 

 shape of the bed also deserves notice ; its general thickness is about 

 fifteen inches, which it preserves for near thirty yards, as appears 

 in the section of the quarry ; it then diminishes at each end to a 

 thin edge, and at length totally disappears. At a short distance in 

 front, there happens to be left by the quarry-men an insulated 

 butt, w'^here this bed is not found at the level where it might be 

 expected ; the conclusion therefore is, that it has terminated also in 

 this direction in a similar manner : thus, as to its figure, putting 

 the practical geologist in mind of the mineral deposit called a pipe- 

 work in the lead countries. I must however observe that in an 

 extensive pit at Kneesworth on the other side of the county, the 

 same bed occurs again, where it preserves an uniform thickness and 

 direction like the other beds with which it is associated. In 

 general, I take this to be the bed which Mr. Townsend* notices as 

 hard and rubbly, and found in descending the hills from Everly to 

 the vale of Pewsey. It has also been observed by Mr. Warburtoii 

 at Marlborough. 



I have never been able to observe any strong^line of separation 

 betwixt the clunch and the succeeding stratum of gault on which 

 it rests. I believe they pass by degrees into each other. The 

 lower beds of clunch become more sandy, and gradually assume 

 the nature of an argillaceous loam. In the next observable stage 

 of transition, the mass assumes a greenish grey colour, and a 

 plentiful admixture of dark green sand is uniformly dispersed 

 through its substance. At the same time it contains numerous 

 irregular dark brown nodules of a ferruginous indurated marl. 

 At length these foreign matters disappear, the mass becomes 

 uniform and ends in the bluish clay or argillaceous marie called 



* A Character of Moses, vol. 1, page 98. 



Vol. III. 2 i 



