GEOLOGY. 37 



and along Southern Europe to the Pyrenees (in fact from Spain to 

 China).* 



In a formation so extensive, the recognition of which is traceable to 

 the original similarity of certain (eocene) conditions, others also may 

 well have occurred at wide lateral intervals, and those resulting in saline 

 accumulations at this period are known to have done so in Europe and 

 elsewhere. 



It is certainly peculiar that in such close proximity here there should 

 be two salt series of great thickness and extent, one of not younger 

 than silurian age, and the other associated with nummulitic rocks, a fact 

 which is of itself suggestive of strange conditions from earliest times 

 having affected the region of the Upper Punjab, if it does not point to 

 an ancient local and recurring source for the mineral. 



The differences pointed out in the character of the salt itself, con- 

 trasted with that of the Salt Range, together with the diversity mark- 

 ing the whole geological section in the two regions, and the difficulty 

 of finding an adequate explanation of the absence here of the great 

 overlying Salt Range series, seems sufficient to warrant the conclusion that 

 the rock-salt deposits of these two regions are of entirely separate age : 

 while the details given and to follow indicate that the Kohat salt, if not, 

 as appears likely, absolutely eocene, is, at any rate, not much older than 

 the base of the nummulitic formation. 



Modern theory of the formation of rock-salt.f — This is hardly the 

 place to dwell at length on the state of geological knowledge regarding 

 the origin of rock-salt masses, which, it appears, may occur in any forma- 

 tion, from the silurian, as in the Alleghany Mountains (Abingdon), 

 Washington Co., Virginia, United States of America, J and in the Punjab, 



# Fisher, Geological Magazine, Vol. X, p. 257. 



f The subjects referred to in this section have frequently been discussed with 

 Dr. Warth. 



X Karsten's work quoted ; also Dana's Mineralogy. 



( m ) 



