ANNIVERSARY ADDRESS OF THE PRESIDENT. 159 



that during the historic period, and within modern times, the sur- 

 face of the Caspian has been diminishing, from the disproportion 

 between the evaporation from so large a surface in that climate, and 

 the sources of supply of water. W hatever portion of the land occu- 

 pied by the Steppe limestone is now on a level with, and below the 

 level of the Black Sea, may have been laid bare by this gradual 

 lowering of the water of the Caspian ; but whatever portion is above 

 that level, and the greatest proportion of it is so, must, it is evident, 

 have been upraised ; and there is abundant proof of volcanic forces 

 being in activity in that region to the present time. To endeavour 

 to trace the direction of the vast body of water that must have been 

 displaced by the upheaved land, as there could be no direct outlet 

 to the ocean, would be an inquiry of great interest ; for it can hardly 

 be doubted that there must be evidence of a deluge or deluges ha- 

 ving swept over a large portion of that part of Asia, and more espe- 

 cially if the elevatory forces acted suddenly. 



As the leading features of the physical structure and the great 

 geological divisions of the continent of North America are well 

 known, I do not think it necessary to give any general outline of 

 the country described by Mr. Lyell in his lately-published ' Travels ' ; 

 but 1 shall have frequent occasion to refer to the information con- 

 tained in that work on several points of great importance, in speak- 

 ing of some of the additions in the past year to our knowledge of 

 the great groups of rocks, and to our better acquaintance with ques- 

 tions of mineral structure, changes in the form of the land, and dis- 

 tribution of organic remains. 



I shall now offer some remarks on the several great groups of for- 

 mations, and shall begin with the lowest fossiliferous deposits. 



Silurian Hocks, 



It is certainly remarkable, considering the short time that has 

 elapsed since Sir II. Murchison first proposed the separation of the 

 lower beds of the palaeozoic strata into one great series, that rocks 

 which appear to be clearly made out to belong to the Silurian system 

 should have been already recognised in so many regions remotely 

 distant from each other. That they constitute a great part of Eu- 

 rope has been shown by many writers. The geologists of the United 

 States and Mr. Lyell have told us how widely they are spread 

 over the northern States of North America ; and we learn from 

 Captain Bayfield that they occur extensively all round Lake Huron ; 

 northward towards Hudson's Bay ; along the nortliern siile of the 

 valley of the St. Lawrence, eastward to tlic strait of Belle Isle, and 

 on the western coast of Newfoundland from that strait to its southern 

 extremity. M. Alcide d'Orbigny has described them as extensively 

 developed in South America; and from Mr. Darwiu we learn that 

 they probably exist in the Falkland Islands, adjoining the farthest 



