ANNIVERSARY ADDRESS OF THE PRESIDENT. IxXXV 



also in the tuff itself. As the sand and comminuted matter ejected 

 from existing volcanos are frequently found to contain infusorial re- 

 mains, it is clear that the volcanic force has acted upon aqueous de- 

 posits lying above it in the interior of the mountain, which it has 

 reduced to powder. It is not therefore an improbable supposition that 

 the blocks on the sides of Somma are fragments of sedimentary strata 

 broken up by the volcanic action and thrown up through the vent. 



In conformity with the plan I have followed in this Address, were 

 there not a sufficient reason in the length to which it has already ex- 

 tended, I ought not to enter upon the consideration of any of the works 

 published in the last year that treat of the older formations ; but I 

 cannot deny myself the satisfaction of calling your attention to the 

 memoir of Sir Henry de la Beche, which I have already alluded to, on 

 the formation of the rocks of South Wales and South-western England, 

 for I consider it the most comprehensive and most important work re- 

 lating to this period in the Geology of England which has appeared 

 since the publication of the * Silurian System' of Sir Roderick Mur- 

 chison. It is the first of the series of essays in the first volume of the 

 * Memoirs of the Geological Survey of Great Britain,' and occupies 

 300 closely printed large octavo pages, so that the mass of information 

 it conveys is immense. Four-fifths of it refer to the palaeozoic rocks, 

 and the igneous rocks associated with them ; in the remainder of the 

 essay there are many valuable details respecting the New Red Sand- 

 stone, for which the author retains the name given by the Rev. Wm. 

 Conybeare of the Poicilitic series, and also respecting the lower parts 

 of the Oolitic series, that occur westward of a line drawn from Lyme 

 Regis to the borders of Shropshire. Even a brief analysis of the 

 most important parts of this essay would extend far beyond the space 

 to which I must limit myself. As a topographical guide and com- 

 panion to the geological map of the Survey, the memoir is invaluable ; 

 and it abounds in proofs how eminently fitted the author is to teach 

 others "how to observe in geology." I know no portion of any 

 country the geology of which has now been more thoroughly examined 

 and described than the west of England ; and I camiot conceive a 

 more instructive or more agreeable occupation for a geologist, whe- 

 ther he be already well- versed in the science, or be a student acquainted 

 only with the elements of it, than to travel through these western 

 counties and South Wales, with the geological maps and sections of the 

 Survey, this volume of memoirs. Sir Henry de la Beche' s former re- 

 port, the joint memoir of Sir R. Murchison and Professor Sedgwick on 

 the Physical Structure of Devonshire, and the 'Figures and Descriptions 

 of the Palaeozoic Fossils of Cornwall, Devon, and West Somerset,' by 

 Mr, Phillips. When he arrives at the places of which they treat, he 

 will also find most valuable assistance from the papers of Austen, 

 Lonsdale, Buckland and Conybeare, that treat of this country. 



Although I am unable to lay before you even an outline of that 

 which may be learned from the study of the memoir of Sir H. De la 

 Beche, I will call your attention to some parts of it which appear to 

 me of special interest. 



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