240 Supplement to Mr. Scdgioick's Paper on the Magnesian Limestone. 



superior to the magnerian limestone is the equivalent of the bunter sandstein ; 

 and a part at least of the variegated marls under our lias may be safely iden- 

 tified with the keuper. 



To the opinions which I have advanced respecting- the origin of the dolo- 

 niitic formations of England*, I attribute very little importance. According 

 to the theory of an eminent continental geologist, the dolomitic portions of the 

 Alps have been produced by a peculiar igneous action subsequent to the deposit 

 of the great calcareous formations to which they are subordinate. Whatever 

 mav be the evidence for this theory in certain alpine regions, it derives at least 

 no support from the facts stated in the preceding paper. The magnesian 

 earth, whatever may have been its origin, was unquestionably an original 

 constituent of the formations above described ; nor is there, I think, any con- 

 ceivable hypothesis to account for its subsequent introduction. 



* p. 123. 

 London, 



October 31, 1829. 



