gS ON THE CONVOLUTIONS OF STRATA, 



be ascribed to the elevation of the central granitic ridge, or 

 whether its arrival at its present place has been connected 

 with their formation, does not appear from any of the facts 

 which 1 have read an account of, or recollect to have seen. 

 It is probable that the point will not be decided, till that 

 country is visited by a person previously aware of the theore- 

 tical views which we have been considering. 



A case of such convolutions is mentioned by M. de 

 Saussuke, at a spot which I remember well, the cas- 

 cade called the Nant d'Arpenaz, on the road to the Gla- 

 ciers of Chaniouni. The strata there consist of limestone, 

 and are bent in such a manner, as to have struck that 

 valuable observer -with the utmost astonishment; yet, in 

 our view, they may easily be accounted for by a lateral 

 thrust. In reasoning upon this subject, he finds himself for- 

 ced to contemplate the possibility of those convolutions ha- 

 ving been the work of subterraneous forces, occasioned by in- 

 ternal fire ; but he abandons the idea almost as soon as he has 

 formed it, from the retlection that this mountain, and its 

 neitrhbourhood, shew no indications of the action of fire. Af- 

 ter a o'ood deal of argument, he at last (though with seeming 

 reluctance), submits to the idea, that these great results 

 may have been the work of crystallization ; the insuflliciency 

 of which reasoning, Mr Playfair, in his Illustrations, 

 art. 207. has clearly pointed out. 



Since this paper was read in the Society, I have met with 

 a very interesting account of a set of rocks in Argyleshire, 

 whose position and arrangement greatly resemble those which 

 I have been describing, and among which, one fact occurs 

 which seems well worthy of notice. (This account is contain- 

 ed in the Edinburgh Encyclopaedia, under the article Ar- 

 gyleshire, and was written by Mr Archibald Camp- 

 bell, 



