Geological Society. 311 



whole chain; but to meet at an angle marked by a great double system 

 of breaks and fissures, one passing in the direction of the eastern, 

 and the other of the western portions of the chain. He further proves, 

 that the system of fissures in the line of the Eastern Alps is more 

 recent than the other system that in the prolongation of this line 

 towards the west, the old diluvial gravel has undergone movements 

 of elevation and that these movements have been propagated to the 

 lacustrine and volcanic regions of Auvergne. 



On a review of the whole evidence, I think he has demonstrated, 

 that there are two distinct deposits of diluvial gravel near a portion 

 of the Western Alps that the colossal mass of Mont Blanc, and at 

 least a considerable portion of the Eastern Alps, were elevated after 

 the deposit of the older diluvium and that the newer diluvium (in- 

 cluding all those enormous crystalline erratic blocks so admirably 

 described by Saussure ) rolled off from the regions of the higher Alps 

 during this last period of their elevation. 



There are six other supposed periods of elevation briefly considered 

 in the researches of M. Elie de Beaumont, each marked by distinct 

 geographical features : but I will not now detain you with their enu- 

 meration. If the generalizations to which I have pointed be true, 

 and, as far as I comprehend them, they seem to be based on an im- 

 moveable mass of evidence, we must then conclude that there have 

 been in the history of the earth long periods of comparative repose, 

 during which the sedimentary deposits went on in regular continuity, 

 and comparatively short periods of violence and revolution, during 

 which that continuity was broken. And if we admit that the higher 

 regions of the globe have been raised from the sea by any modifica- 

 tion of volcanic force, we must tKen also admit that there have been 

 several successive periods of extraordinary volcanic energy. 



How we are to escape from this conclusion I am unable to com- 

 prehend, unless we shut out the evidence of our senses. Of volcanic 

 powers we know nothing, except during the irregular periods of their 

 activity and returning periods of intense activity, after long ages of 

 comparative repose, may be among the enduring principles in the me- 

 chanism of nature. I do not throw this out as even a probable hypo- 

 thesis j but it is, at least, as probable as any other hypothesis un- 

 founded on the evidence of geological phenomena. 



That the system of M. Elie de Beaumont is directly opposed to a 

 fundamental principle, vindicated by Mr. Lyell, cannot admit of 

 doubt. And I have decided to the best of my judgement, in favour 

 of the former author, because his conclusions are not based upon any 

 a priori reasoning, but on the evidence of facts ; and also, because, in 

 part, they are in accordance with my own observations*. 



* For example ; the vertical position of the green-sand and chalk on the 

 eastern flank of the Hartz mountains, and the horizontal position of the same for- 

 mations on the flanks of the Erzgebirge, were remarked by Mr. Murchison and 

 myself in the summer of 1829. During the same tour we had repeated proofs of 

 the recent elevation of the chain of the Eastern Alps ; of the high elevation of the 

 green-sand series in the calcareous chain to the north-east of Trieste ; and of the 

 horizontally of the tertiary deposits of Styria. All these facts (of which we did 

 not at the time comprehend the whole importance) harmonize with the system of 

 M. de Beaumont. 



Let 



