212 Dr. Gil by on the Magnesian Limestone , &V. 



ments, forming in fact a hard compact magnesian limestone. This 

 variety will give 36 or 38 per cent, of carbonate of magnesia. All 

 the varieties are of a yellow colour, and like the magnesian lime- 

 stone of the north, it often exhibits black spots throughout its 

 substance, and it frequently contains impressions of shells. 



The analysis of the compact variety, 



conducted in the usual 



ly, gave me of 





Carbonate of lime . 



53.5 



Carbonate of magnesia , 



37.5 



Oxyd of iron . . 



.8 



Insoluble matter . . 



. 7. 



Loss 



. 1.2 





100.0 



Now with regard to its geological relations, it in no respect 

 differs from the limestone conglomerate which I have mentioned 

 as the lowest bed of the red ground formation. I have traced it 

 in a continued line by the sea side from Portishead to Clevedon, 

 and it every where contains the same fragments and every where 

 lies horizontally and unconformably upon the inclined strata (which 

 are there the old red sandstone,) in the same way that the usual 

 red grained conglomerate does. It is therefore plainly to be con- 

 sidered as the lowest stratum of the red ground formation, and 

 consequently succeeds immediately to the coal deposit. 



It seems to me that the magnesian limestone of the north of 

 England may be referred to the same formation. In Thomson's 

 Annals there is lately a short notice of a paper read before the 

 Geological Society by Mr. Winch, upon the magnesian lime- 

 stone in the north of England, in which it is stated that the Tees 



