AND ASSOCIATED PERMIAN KOCKS OF DURHAM. 221 



material are numerous hard concretions, some of which are merely 

 of hard limestone, others in the centre pass into a highly siliceous 

 and flint-like suhstance. It is the powdery limestone only that 

 has heen analysed. Mr. E. C. Clapham has already published 

 an account of the analysis of the siliceous concretions.* 



ANALYSIS. 



Carbonate of lime 42-48 



magnesia 49"86 



Sand, clay, oxide of iron 6*60 



Water, &c 1-06 



100-00 

 No. 36. Locality— GALLEY'S GILL, 



SUNDERLAND, 



Lithological Characters. — Grey and yellowish, hard, crystalline, 

 with numerous irregular cavities sometimes coated with calcite ; 

 unfossiliferous. 



ANALYSIS. 



Carbonate of lime 95'29 



magnesia 2-91 



Sand, clay, oxide of iron, &c 1'40 



Water, &c 0-40 



100-00 



Has heen extensively wrought and burnt for lime for many 

 years. Some portions of the rock pass into a soft marl resembling 

 No. 35 ; and this has been almost as largely worked as the other, 

 and used in the manufacture of bottles on the Wear and Tyne. 



The Middle Limestone is not considered to make a good tillage 

 lime. It is generally described as being "too hot," owing to the 

 large quantity of carbonate of magnesia it contains. This is 



♦analysis. 



Silica 965 



Alumina and iron 1"2 



Carbonate of lime I"6 



magnesia trace. 



99-3 

 Trans. Tynes. Nat. Club. Vol. V, p. 124. 



