1851.] HOPKINS ON CHANGES OF CLIMATE. 91 



much increase, the temperature of the region corresponding to the 

 present shores of the Arctic Sea ; for nearly the whole of that mass 

 of warm water, which now elevates so remarkably the temperature 

 of the northern Atlantic up to the North Sea, would then proceed 

 to discharge itself into the Arctic Sea between the Rocky Mountains 

 and Hudson's Bay, by a course shorter, more direct, and probably 

 therefore more rapid, than that by which it now reaches the coast of 

 Iceland. I should consider it most probable that it would produce 

 a temperature in the region along the north-eastern flank of the 

 Rocky Mountams, and extending to the present northern shores of 

 the American continent, higher than that of Iceland, and more nearly 

 resembling that of some parts of our own island. 



After having arrived at this conclusion, I was naturally anxious to 

 learn whether any distinct indications had been observed of this cli- 

 matal condition of the region in question, and recollecting to have 

 heard my friend Prof. E. Forbes make incidental mention of the dis- 

 covery in high northern latitudes of vegetable remains indicative of 

 a temperature considerably higher than the existing temperature, I 

 wrote to him, stating my own conclusions, to ascertain the precise 

 locality in which these remains had been found, and the period to 

 which they belonged. A few days ago I received his reply, stating 

 that these plants might belong to the pleistocene period, and that 

 the locality in which they had been found was precisely that above 

 spoken of, along the flanks of the Rocky Mountains and between 

 them and Hudson's Bay, as the region of which the temperature 

 would probably be so much affected by the warm current from the 

 Gulf of Mexico. I cannot but regard these remains as strongly con- 

 firmative of the view which I have now ventured to propound. 



But how, it may be asked, could such a warm current be consist- 

 ent with the glacial phsenomena of the North American continent ? 

 I have already intimated the reply to this question. The exact pe- 

 riod of these phsenomena might be either anterior or posterior to that 

 during which the Gulf-stream made its way to the Arctic Sea. Sup- 

 pose the superficial configuration of that continent previous to its 

 submergence to have been similar to its present configuration. A 

 gradual subsidence might convert the northern portion of the conti- 

 nent into an arctic sea long before a free north-western course would 

 be opened for the Gulf-stream. With the exact similarity of the 

 former and present configuration, this extended arctic sea would be 

 bounded towards the south by the higher land which now constitutes 

 the watershed between the great northern valley of the chain of 

 lakes and that of the Mississippi ; but if the former and present con- 

 figurations of the land were only approximately and not accurately 

 similar, or if the submergence were more rapid in the north than in 

 the south, the boundary of the extended Arctic Ocean might pass 

 further to the south, and comprise, for instance, the northern part 

 of the valley of the Mississippi, before the Gulf of Mexico extended 

 its waters much to the north of its present boundary. In like man- 

 ner, similar conditions might obtain during the subsequent emergence 

 of the land. Minor hypotheses of this kind, entirely subsidiary to 



