418 A Geognostkal Sketch of [Dec. 



got had been cut into long thin plates, and consisted of two layers, 

 each about one-eighth of an inch thick, lying upon each other, but 

 admitting of an easy separation. These thin plates are very flexible. 

 When held by the two extremities the middle bends several inches; 

 but it does not possess the smallest elasticity. 



Colour cream-yellow, differing in intensity in different parts ; 

 some specimens have nearly a tile- red colour, and here and there 

 streaks or bands of this colour occur in the cream-yellow similar to 

 what we observe in ribbon jasper. 



Fracture even, earthy; soft; cannot be scratched by the nail, 

 but yields very easily to the knife ; the fracture in the great is pro- 

 bably slaty. 



Lustre dull; opake; fragments indeterminate; specific gravity 

 2-54 1 ; but as the stone is porous, this is probably below the truth. 

 Its composition 1 found as follows : — 



Carbonate of lime 62-00 



Carbonate of magnesia 35*96 



Insoluble matter 1*60 



Loss 044 



100-00 



It dissolves in acids as readily as common carbonate of lime. 



This magnesian lime-stone has been long burnt in prodigious 

 quantities in the neighbourhood of Sunderland, and sent coastways 

 both to the north and the south. It goes in great abundance to 

 Aberdeenshire. As no complaints have ever been made of its being 

 injurious when employed as a manure, it would be curious to know 

 whether this circumstance be owing to the soil on which it is put, 

 or to the small quantity of it used, in consequence of its price, 

 occasioned by the long carriage ; for it appears from Mr. Tennant's 

 statement that at Ferrybridge the farmers are aware that it does not 

 answer as a manure so well as pure carbonate of lime. 



In the preceding rapid sketch I have taken no notice of some 

 small patches of the newest floetz trap which occur towards the 

 north-east parts of Northumberland. I examined several of these 

 places about four years ago, and found them to consist of green- 

 stone rocks seemingly deposited above the Independent Coal For- 

 mation. This is the case with the rock on which the castle stands 

 in Holy Island. The basis of this island is lime-stone. The same 

 thing occurs at Bamborough Castle, and in several hills in the 

 neighbourhood of Belford. These facts may have some interest to 

 the geologist, though I did not consider them as of sufficient im- 

 portance to interrupt the very general view of the structure of these 

 counties which I have now given. 



I shall terminate this essay with a list of some of the most re- 

 markable terms connected with mineralogy peculiar to the counties 

 •f Northumberland, Cumbeiland, and Durham; and I shall give 



