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chance, either of limiting or extending his own principles, as might 

 seem good during the advances of our science. What he has written 

 with so much power, must inevitably produce a great impression on 

 the English school of geology. It is on this account, and not with any 

 spirit of unfriendly criticism, that I have discussed, at greater length 

 than I first intended, the points on which we differ ; and I am only 

 anxious, that a work abounding in so many admirable details, should 

 hereafter appear, as far as any human production can do, without a 

 blemish in the enunciation of a single principle. 



Greatly as I admire the generalizations of M. de Beaumont, they 

 have, I think, been already pushed too far. We may follow them as 

 our guides, but they must never take the place of direct observations. 

 It is only through limited regions of the earth that we shall perhaps be 

 ever able to make out the true parallels of contemporaneous elevation. 

 Distant continents may have independent parallel systems of eleva- 

 tion. In several mountain chains (for example, in the Eastern Alps) we 

 have direct proof, that the forces of elevation have acted on the same 

 line at successive epochs ; and in our island, there have been move- 

 ments of elevation at different epochs, yet on lines which are parallel. 

 Lastly, lines of elevation (like the existing lines of modern volcanic 

 vent) may, in their prolongation, have deflected far from their first 

 direction. But I must forbear, for the discussion of these questions 

 would lead me into endless details*. 



At our former Anniversary I ventured to affirm, that our diluvial 

 gravel was probably not the result of one, but of many successive 

 periods. But what I then stated as a probable opinion, may, after the 

 Essays of M. de Beaumont, be now advanced with all the authority of 

 established truth : and among the many obligations we owe to this 

 accomplished observer, I may mention the new and instructive views 

 he has given us of the origin of the great masses of old detritus lying 

 scattered over the lower regions of the earth. We now connect the 

 gravel of the plains with the elevation of the nearest system of moun- 

 tains ; we believe that the Scandinavian boulders in the North of 

 Germany are of an older date than the diluvium of the Danube; and 

 we can prove, that the great erratic blocks, derived from the granite 

 of Mont Blanc, are of a more recent origin than the old gravel in 

 the tributary valleys of the Rhone. That these statements militate 

 against opinions, but a few years since held almost universally 

 among us, cannot be denied. But theories of diluvial gravel, like 



* That part of the generalizations of M. Elie de Beaumont, in which he seems 

 to assume, that each great period of elevation was followed by a great change in 

 organic forms, is, perhaps, the least secure. In England, there is a great break be- 

 tween the greywacke and carboniferous systems ; yet the fossils, in the calcareous 

 groups, alternating with the greywacke, very nearly approach to those of the car- 

 boniferous limestone. There is also a great break between the carboniferous and 

 magnesian limestone series of this country ; but their suites of fossils very nearly 

 resemble each other, and several species are common to both. Again, on the 

 outskirts of the calcareous zone of the Alps, there are large groups of strata, with 

 fossils conforming both to the secondary and tertiary type. I must, however, 

 add, in justice to the author, that his observations on the changes of or- 

 ganic forms, are casually thrown out, here and there, and do not seem to form 

 any essential portion of his theory. 



