PRIMARY LIMESTONE. 209 



fact at Cearp in the Pyrenees, elsewhere noticed, where 

 the shells become gradually obliterated, with the cor- 

 responding acquisition of a crystalline texture in the 

 rock, where it is in contact with granite. The bitu- 

 minous strata in primary limestone, just noticed, may 

 serve to confirm the same views ; since, it is unques- 

 tioned, that in the secondary limestones, this character 

 is derived from organic bodies. 



As limestone occurs in every situation,, from the 

 most antient of the primary to the most recent of the 

 secondary, and even of the tertiary strata, it must be 

 considered the most universal rock in nature. At the 

 same time, it presents fewer differences of character, if 

 we except the adventitious imbedded bodies, than any 

 other: a consequence arising from that comparative 

 simplicity and chemical composition under which it 

 has evaded that action of heat which has changed the 

 characters of the other primary strata. 



Primary limestone occurs in this country in masses 

 so small that they can give no character to a district ; 

 and there is no reason to believe that it is more abun- 

 dant in other parts of the world. This has indeed 

 Been often asserted ; but, doubting the accuracy of 

 that opinion, I must refer the student to the works in 

 question ; cautioning him to bear in mind, that no 

 limestone can be deemed primary, from any thing 

 short of a clear proof that it alternates with primary 

 strata. 



In the larger, as in the smaller portions, Primary 

 limestone is disposed in beds, like the rocks which it 

 accompanies ; but these are sometimes so obscure that 

 their stratification can scarcely be traced : a conse- 

 quence, probably, of the fusibility of this rock, and of 

 the influence to which it has in these cases been sub- 

 jected. In the only manner in which it is known in 



VOL. n. p 



