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On the Theory of the Elevatimi of Mountain Chains, as advo- 

 cated by M. Elie de Beaumont. By Dr Boue. Communi- 

 cated by the Author. 



In Brochant's excellent French translation of De la Beche's 

 Geological Manual, M. de Beaumont has given a new and mo- 

 dified exposition of his theory and opinions, in regard to his 

 twelve or thirteen epochs of elevations or revolutions. His essay 

 may be considered as consisting of two parts, viz. an explanation 

 of the theory, and an account of the application of his system. 



It is only to Mr Lyell that M. de Beaumont seems to stand 

 opposed in the first part of his essay. Every one knows and 

 acknowledges that most of the upheavings (redressemens) were 

 produced by a series of violent and rapid movements ; and this 

 view is rendered more probable by the extent of the effects of 

 elevation. In treatises and lectures on Geology, the Pyrenees, 

 the primary chains of Scotland, and some chains of Scandinavia, 

 have sometimes been brought forward as examples of this kind ; 

 and M. de Beaumont acknowledges this very fairly (p. 167). 

 On the other hand, Mr Lyell has shewn very well the vagueness 

 of the Hmits assigned by M. de Beaumont to his revolutions. 

 (See Principles of Geology, vol. iii. p. 343.) 1 believe that few 

 geologists would blame M. de Beaumont for rejecting Mr 

 LyelPs hypothesis, by which he endeavours to explain the up- 

 heavings, by the unlimited repetition of local and slow move- 

 ments ; although this view may be correct in the case of the ele- 

 vation of whole continents. 



It must always be difficult to trace limits between a very 

 quick and a very slow movement ; as, for example, when one 

 speaks of an elevation which has taken place rapidly, does he 

 mean an instantaneous upheaving ? or are we to understand an 

 effect produced in a space of some months, or some years, or 

 even some centuries .? An upturning of strata may have taken 

 a considerable time for its completion ; and even such a period 

 as to have admitted of the deposition of strata on a part of the 

 earth different from that where the elevating force was in action. 

 In this way the geological demonstrations of the great revolu- 



