34 



The present specimen, given me by Mr. Pilkington, 

 F. L. S., was found about 1 90 feet deep, in dicing a well 

 for Lord Redesdale, now C. Poole's, Esq., at Streatham, 

 Surry. 



It is of a semi-indurated toughish texture, but readily falls 

 to pieces in a damp atmosphere. The clayey parts are evi- 

 dently mixed with carbonate of lime, and some of the shells 

 are little else, although they retain their original figure so 

 well that we may distinguish some of the species*. The 

 pearly oyster shells only seem to have assumed a black tinge. 

 'The other pearly shell, perhaps Area Nucleus, Linn. Gmel. 

 v. I. 3314. retains its original lustre, its gluten being less 

 easy to decompose f. There are other pearly shells in the 

 mass, but not easily to be made out. The clayey-looking 

 part does not effervesce with vinegar, neither do the pearly 

 shells. The chalky ones readily do. Maries depending on 

 their proportions of lime, clay J, or sand, are used as manures, 

 each sort being adapted to the nature of the land they are 

 applied to. 



One kind of marie has lately been found to be a useful 

 stucco, when properly prepared. 



* These, on breaking the mass, leave h;4f their substance on the convex 

 side of the matrix, and the other half in the mould. 



f See Mr. Hatchett's ingenious paper in Philosophical Transactions 

 for 1798. 



+ Chy must be understood as a mixture here of argil, silex, and iron. 



