Ch. XXIII.] SUPPOSED UNIVERSALITY OF RED MARL. 333 



stratum, and even if these abound and are specifically different 

 from the fossils of the supposed European equivalent, it may 

 be objected, that we cannot expect the same species to have 

 inhabited very distant quarters of the globe at the same time. 



Supjwsed universality of red marl. We shall select a remark- 

 able example of the erroneous mode of generalizing now alluded 

 to. A group of red marl and sandstone, sometimes containing 

 salt and gypsum, is found in England interposed between the 

 lias and the carboniferous strata. For this reason, other red 

 marls and sandstones, associated some of them with salt and 

 others with gypsum, and occurring not only in different parts 

 of Europe, but in Peru, India, the salt deserts of Asia, those 

 of Africa, in a word, in every quarter of the globe, have been 

 referred to one and the same period. The burden of proof is 

 not supposed to rest with those who insist on the identity of 

 age of all these groups, so that it is in vain to urge as an ob- 

 jection, the improbability of the hypothesis which would imply 

 that all the moving waters on the globe were once simulta- 

 neously charged with sediment of a red colour. 



But the absurdity of pretending to identify, in age, all the 

 red sandstones and marls in question, has at length been suf- 

 ficiently exposed, by the discovery that, even in Europe, they 

 belong decidedly to many different epochs. We have already 

 ascertained, that the red sandstone and red marl with which 

 the rock-salt of Cardona is associated, may be referred to the 

 period of our chalk and green-sand *. We have pointed out 

 that in Auvergne there are red marls and variegated sand- 

 stones, which are undistinguishable in mineral composition, 

 from the new red sandstone of English geologists, but which 

 were deposited in the Eocene period ; and, lastly, the gypseous 

 red marl of Aix in Provence, formerly supposed to be a marine 

 secondary group, is now acknowledged to be a tertiary fresh- 

 water formation. 



* I was led to this opinion when I visited Cardona in 1330, and before I was 

 aware that M. Dufrenoy had arrived at the same conclusions. Ann. des Sci. Nat., 

 Avril, 1831, p. 449. 



