18 



by its strong blaze in a common fire. It is sometimes sold 

 for a guinea per ton, and is often in large broad masses, 

 three or four feet in diameter. It is also sometimes dug 

 from the rock with a clay shovel. 



The upper specimen is somewhat slaty in fracture, though 

 rather more earthy. It is a softish clayey Shale with much 

 Petroleum, and emits the smell peculiar to the latter sub- 

 stance when heated. 



The lower specimen is still more earthy, but somewhat 

 fissile, and is, as it were, interrupted with regard to its 

 parallels by partly curving round an irregular ball of earthy 

 Pyrites. It is a curious specimen ; — sometimes Carbonate 

 of Lime or Chalk intervenes, which is soft. Many other 

 varieties occur, some of which are more slaty, some more 

 earthy, and others of different colours. 



The Isle of Wight, opposite Alum Bay, affords Bitu- 

 minous Carbon in great variety. My kind friend Mr. Lyell 

 favoured me with some that seems to point out the progress 

 of the Bitumen passing from the vegetables and im- 

 pregnating the substances near them. Lincolnshire affords 

 a similar substance, with Lime of shells remaining betwixt 

 the laminae. I have some sent me by the Rev. R. B. Francis. 



A mixture of Bitumen with Lime, Clay, &c. is some- 

 times found in Essex, nearly resembling this. I have been 

 favoured with it by Colonel Walford. 



