the age of Tertiary Deposits. 115 



Mr. Charlesworth, who appears to have lately paid consi- 

 derable attention to the examination of the crag,* and who 

 has offered many objections to the employment of the pro- 

 portional number of analogous species, in determining the 

 ages of the tertiary strata ; among others, that of the possible 

 introduction of the fossils of one stratum, into an adjoining 

 one, proposes, it is true, to distinguish two formations in the 

 English crag, the lower, or coralline crag, and the upper, or 

 red crag, as belonging to two different periods. But there 

 appears to exist between them so intimate a union, that their 

 separation does not seem to me more admissable, than that 

 which we might also propose in the basin of the Loire, be- 

 tween the beds of littoral crag, composed of broken shells, 

 and those of calcareous coral, deposited under calmer waters, 

 and which appear generally lower. 



It is, then, with the entire deposit of crag, that we must 

 compare the deposit of the faluns. Now, to resume our argu- 

 ment, the following is a statement of the present state of di- 

 verging opinions with regard to this subject. 



The faluns, according to M. Deshayes, contains 19 per cent."\ of 



according to M. Dujardin, 50 - V analogous 



The English crag, M. Deshayes, - 50 - -j species. 



Dr. Beck, no analogous species. 



Consequently, if we admit the separate results of M. Dujar- 

 din, who has not, it is true, studied the crag, and of Dr. Beck, 

 who has not studied the faluns, but who have each based 

 their judgment upon the examination of a great number of 

 species of each deposit, unmixed with those of any other ba- 

 sin, even of basins supposed to be contemporaneous, we must 

 conclude from them, that the faluns are as recent as the sub- 

 appennine hills, and the upper stratum of Sicily ; and that 

 the crag is not only more recent than the faluns, but, by the 

 mere application of the law of the proportional number of a- 

 nalogous species, will descend into the lower formation of 

 Paris and London. I am far from admitting all these conse- 

 quences, especially the last ; and I do not doubt that in de- 

 fault of perfect identity, we ought to reckon a greater or less 

 analogy between the fossils of different basins, and the recent 

 species, as M. Defrance formerly proposed. It is also very 

 possible, that if Dr. Beck had examined the fossil shells of 

 the faluns, he would not have recognised there anything like 

 so many analogous species as M. Dujardin; and that if the 

 latter had studied those of the crag, he would have pointed 



* Proceedings of the Geological Society, No. 41. — Edin. Phil. Jour. 

 [Taylor's] October 1836, and January 1837.— Loudon's Mag. Nat. Hist. 

 Nos. for Jan. and Feb. 1837. 



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