154 



COTEMPORANEOUS ROCK FORMATIONS. 



have been raised together, when that part of England entierged from 

 the ocean ; unless the red ntiarl was formed in a mediterranean lake 

 or sea, surrounded by distant high ground. Adopting this view of the 

 subject, though w^e may be certain that the beds of granite in England 

 were elevated before those of the Alps, it does not follow that Eng- 

 land must necessarily have been dry land, before the Alps of Savoy. 

 Since, therefore, the elevation of the beds in mountain ranges, may 

 have preceded their final emergence above the ocean, this consider- 

 ation deprives the investigation into the relative antiquity of the eleva- 

 tion of the beds in mountain ranges of much of its value. 



Before proceeding to describe the secondary and tertiary forma- 

 tions, I shall offer some preliminary observations, connected with the 

 enquiry respecting the relative age of the different beds. Where a 

 similarity of mineral character, and a similar association with other 

 beds is observed in different districts, we may sometimes infer that 

 their origin was cotemporaneous ; but when the organic remains are 

 also the same in both, we attain a full conviction of the fact. 



It will not be denied that the chalk and oolite in Yorkshire, were 

 cotemporaneous with certain parts of the chalk and oolite formations 

 in the southern and western counties. In the same manner, we may 

 admit, that the chalk, and oolite, and lias, on the opposite side of 

 the Channel, in France, are cotemporaneous with similar formations 

 in England, with which they preserve an identity of mineralogical 

 and zoological characters. Having once traced these formations to 

 the north of France, we may admit their identity with similar forma- 

 tions, preserving the same identity of character through many of the 

 inland departments of France, and to the Salins at the foot of the Jura 

 range. Over so large an extent of country we may expect to find, 

 as we do in distant districts in England, that certain parts of a series 

 which occur in a certain formation in one place, are wanting in 

 another. In France, some beds occur, under the lias, for instance, 

 which have not hitherto been found in Great Britain : but making al- 

 lowance for such partial variations, we cannot hesitate to admit the 

 identity of the formations in both countries, and also their identity of 

 age. When we enter the Jura, or the great calcareous ranges of the 

 Alps, the enormous thickness of the beds, which are frequently inac- 

 cessible, and the indurated and subcrystalline texture which they of- 

 ten assume, present considerable difRcuhies, if we attempt to identify 

 them with well known formations. Much confusion and contrariety 

 may be observed in the classification of these rocks by different geolo- 

 gists ; but this has arisen partly from the observers not being thoroughly 

 acquainted with the formations with which they were to make the 

 comparison, and partly from the vague and contradictory use of the 

 terms Alpine limestone ( calcaire Alpin ) and Jura limestone ( calcaire 

 de Jura.) There is, however, in some parts of these mountains, 

 both an identity of mineral and of zoological characters, with some 

 of the formations in the upper secondary strata in England. A thick 



