on the ClassiJicatio7i of the European RocJcs. 191 



forward : — " When we institute a more detailed comparison 

 between the various strata, and those remains of animals which 

 they contain, we presently perceive that this ancient sea has 

 not always deposited mineral substances of the same kind, nor 

 remains of animals of the same species ; and that each deposit 

 has not extended over the whole surface which it. covered. There 

 has existed a succession of variations; the former of which 

 alone have been more or less general, while the others appear 

 to have been much less so. The older the strata are, the more 

 uniform is each of them over a great extent ; the newer they 

 are, the more limited are they, and the more subject to vary at 

 small distances. Thus the displacements of the strata were 

 accompanied and followed by changes in the nature of the 

 fluid, and of the matters which it held in solution ; and when 

 certain strata, by making their appearance above the waters, 

 had divided the surface of the sea by islands and projecting 

 ridges, different changes might take place in particular basins." 

 Might not Cuvier have had in his mind, at the writing of this 

 last sentence, the differences observed between the London 

 and Paris basins? And ought we then to profess to detect " the 

 London clay" in the Burman empire ? Far, therefore, from ex-; 

 pecting to find the same series of beds in a distant country, 

 which exists in our own, should we not rather look for another 

 bearing no analogy to it? — Each bed differing from the one 

 of the same probable age in our own series, both from its mi-r 

 neralogical character being altered more or less by accidental 

 circumstances, and its organic contents being those of another 

 latitude, which have existed in a temperature and under circum- 

 stances probably highly different from those of our own climate? 

 I would fain take this opportunity of considei'ing the subject 

 more fully, were it not that I feel conscious of my inability 

 to do justice to it, even in the present state of our obser- 

 vations of the earth's surface. I will therefore, for the pre- 

 sent, do no more than offer a few observations on the two first 

 groups of Mr. De la Beche's classification of our rocks. In 

 the outset, as he has professed to lay down a new classifica- 

 tion, I cannot help regretting he should have kept up the terms 

 " alluvial " and " diluvial," which in my opinion, and I think in 

 that of many of your readers, are as hurtful to true geological 

 science, as any that have yet been invented, and conducive to 

 more mistakes and confusion than even the theoretical division 

 of rocks into primary, transition, &c., which he himself has 

 seen the necessity of doing away with. Furthermore, 1 must 

 confess I do not see the accuracy of the division of these two 

 groups, speaking relatively to their order in the geological 

 series. By tiie "alluvial group," I presume he means a group 



of 



