311 



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 then 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*. 

 ,* Let me not, however, be misunderstood. I have been offering no 

 general criticism of Mr. Lyell's work : 1 have merely been arguing 

 against the extension of one hypothetical principle (an important 

 one indeed in the interpretation of geological phenomena) on which 

 we differ in opinion. Nineteen twentieths of his work remain un- 

 touched by these remarks. His excellent and original historic narra- 

 tive — his dignified philosophic views and clear descriptions — his ad- 

 mirable account of the effects brought about by the great causes, 

 whether aqueous or igneous, now acting on the crust of the globe, 

 contribute to make his volume, in the highest degree, both popular 

 and instructive ; and I cannot but express a wish, that, in the future 

 editions of his work, the system of " geological dynamics" may be 

 stripped of even the semblance of hypothetical assumption ; and that 

 having first ascertained by a mere appeal to facts, what the powers 

 of nature now are (and 1 know no one more competent to the 

 task), he will then proceed to apply them to the solution of the 

 dark problems of geology. This arrangement would not only be the 

 most fair and logical, but would take away that controversial cha- 

 racter, by which, in my opinion, some pages of his present volume are 

 disfigured j and would, in the end, give him incomparably the best 



* 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 

 horizontality 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. 



