816 SIR J. W. DAWSON ox THE EOZOIC AIS'D PAL.^OZOTC 



the Lias to the Eocene, and these belong rather to the Arctic basin 

 than to that of the Atlantic *. In this respect the maritime region 

 of Canada differs materially from that of Europe, though it is note- 

 worth)' that the extreme coastal region of Great Britain to the west 

 is also somewhat deficient in such rocks. 



The question of Palaeozoic climates in the northern hemisphere 

 has some bearings on the subjects discussed in this paper, and is well 

 illustrated by a map of the Arctic districts of Canada recently issued 

 by the Geological Survey t. From this it appears that there are no 

 indications of a warm climate in the Arctic basin up to the close of 

 the Cambrian. The later Ordovician and the Silurian were, however, 

 signalized by the deposition in the Arctic seas of thick and extensive 

 organic limestones, holding fossils comparable with those of the 

 temperate regions at the same time. The Lower Erian may perhaps 

 indicate a short relapse to cold ; but in the Upper Erian and Lower 

 Carboniferous we have warm seas tenanted by marine animals and 

 a rich land-vegetation appearing both in the Arctic Islands of 

 Canada and in Spitzbergen. The Upper Coal-formation and the 

 Permian and Trias indicate a return of cold, and the temperature 

 seems to increase in the Jurassic, attaining its maximum in the 

 later Cretaceous and Eocene, and gradually diminishing to the glacial 

 age, between which and the modern there seems to have been a 

 warm period of short duration, evidenced in the deposition of mam- 

 moth bones, &c., on the Arctic coasts. The cycles of cold and warm 

 climate thus indicated in the Arctic region have. I think, an important 

 bearing on the succession of life further south, at least in Eastern 

 America, and their correlation with the climatal changes in Europe 

 would be a subject of much interest, on which, however, I do not 

 feel in a position to speak positively ; but I imagine that the warm 

 and cold periods will be found to correspond with those of the Arctic 

 basin and of America. 



The general sketch above given is sufficient to show that in the 

 rocks from the Laurentian to the Trias inclusive we have on the two 

 sides of the Atlantic a continuous parallelism in the following 

 points : — 



1. In mineral character and order of succession of aqueous deposits. 



2. In the occurrence of great earth-movements of elevation, de- 

 pression, and plication, at corresponding times. 



3. In the ejection of like kinds of igneous rocks in connexion with 

 like members of the aqueous series. 



4. In the order of introduction and extinction of animals and 

 plants. 



5. In the specific identity of animals and plants in correspondiug 

 formations. 



All this, I think, points to an actual contemporaneity of the suc- 

 cessive changes on the two sides of the Atlantic basin, and to a 

 special correspondence of the formations of the respective marginal 



* For references see ' Notes on Geological Map of Northern Canada ' by 

 Dr. G. M. Dawson, 

 t ' Geology of Northern Canada,' Dr. G. M. Dawson, 1887. 



