117 



covered by the cretaceous rocks with fucoids ; and the greensand of 

 Nice, formerly described by Sir Henry de la Beche, is now shown to 

 repose on the Neocomian limestone of foreign geologists, a formation 

 which, as has been stated, there is reason to think is the represen- 

 tative wholly or in part of our lowest greensand. 



^ Nor has M. Sisnionda neglected the Tertiary deposits ; for by the 

 aid of fossils he has clearly established, that two only of the great 

 epochs of Mr. Lyell are represented in Piedmont ; viz. the Miocene 

 the strata of which are extremely dislocated, and the older Pliol 

 cene or sub-Apennine, which is for the most part horizontal, marking 

 however, by partial breaks, the period of elevation of the Eastern 

 Alps, whilst the Miocene beds ai-e thrown up in the direction of the 

 Western Alps. In reference to this point, M. Sismonda has traced 

 m the Alps, the signs of five distinct and well-separated periods of 

 revolution or upheaval ; and among the agents which have effected 

 the changes, he particularly shows, that whatever part the serpentine 

 may have played in these convulsions, it existed before the accu- 

 mulation of the Miocene deposits, since fragments of that rock 

 abound in the highly inclined pebbly beds of the Superga at Turin. 

 Such, Gentlemen, is a very brief sketch of some of the prominent 

 results of the researches of M. Sismonda ; and admiring, as you must 

 the ability and perseverance with which he has accomplished them' 

 you will, I am sure, feel gratified in seeing that the sedimentary 

 rocks named by the early school of British geologists in our own 

 little island, have served as the base-lines or types by which order 

 has been elaborated in a great disturbed region, M'here the chaotic 

 assemblage of rocks and their crystalline and metamorphic cha- 

 racters seem.ed to forbid the hopes of any such comparisons. 



North American Geology. 



In considering this branch of my subject it will not be expected 

 that I should attempt to give even tlie slightest sketch of the la- 

 bours of all the men of science who constitute the enlightened 

 school of geologists which has arisen within the United States. 

 Possessed of a theatre of research in which natural pheenomena are 

 developed on a gigantic scale, the rapid progress of our transatlantic 

 brethren has been most surprising; and the triumphs which they 

 have achieved are doubly gratifying to ourselves, as they are 

 founded, for the most part, on comparisons of their own rocks with 

 those which have been classified in the British Isles. The past year 

 has been unusually prolific in such communications, and I have 

 therefore confined the following remarks to those researches which 

 have been distinctly brought before us, referring my hearers who 

 wish to study the subject of North American geology in extenso, to 

 the origmal works, already forming a considerable library, including 

 a vast number of communications which are to be found in that 

 excellent periodical, the ' American Journal of Science,' conducted 

 by Professor Silliman. 



Pal(Bozoic Rocks — The value of the remarks of Professor W. B, 



