1851.] HOPKINS ON CHANGES OF CLIMATE. 71 



The isothermal of 32° F. would pass nearly through Madrid. The 

 whole climate of western Europe would be converted into an extreme 

 continental climate similar to that of north-eastern Asia at present. 



16. The last hypothetical case I propose to consider is that in 

 which all the lower land of Europe should be submerged beneath the 

 surface of the ocean. This tract would comprise all northern Europe 

 except the momitainous parts of Scandinavia ; nearly the whole of 

 Russia in Europe, extending southward to the Black Sea ; togethei 

 with Central and Western Europe as far as the Pyrenees, the Alps 

 and the Carpathian Mountains, except those limited ranges of higher 

 land which might still protrude as islands above the surface of the 

 ocean. This space is intended to include all that over which the sea 

 of the period of the Northern Drift must once have extended (sup- 

 posing the drift to be of submarine origin), together with such fur- 

 ther extension southward as may be rendered probable by the confi- 

 guration of the existing surface of the land. I shall also assume the 

 entire absence of the Gulf-stream. I shall consider hereafter the 

 manner in which this great current may have been arrested, or di- 

 verted from its present course. 



In discussing the positions of the isothermal lines for the northern 

 hemisphere in this case, we may again commence with the January 

 line of 32° F. There appears no cause for any material alteration in 

 its position in southern Asia east of the meridian of about the 70th 

 degree of longitude. To the west of that meridian the influence of 

 the ocean extending to the Black and Caspian Seas would doubtless 

 begin to deflect it towards the north, and probably somewhat more 

 than I have supposed it to be inflected by the Atlantic, independently 

 of the effect of the Gulf-stream. From the 30th or 40th degree of 

 east longitude it would proceed nearly west, but Avith a sUght deflec- 

 tion to the south, arising from the influence of the land which we 

 may suppose still to exist in Scandinavia, and also from that of the 

 northern continent of Greenland. This would cause the isothermal 

 to intersect the line of the existing French coast about its north- 

 western extremity, the point at which I have before supposed it to 

 be intersected by the line of 32° F. in the absence of the Gulf-stream. 

 (See Map.) In the region of North America the isothermal would 

 depend on the manner in which the Gulf-stream should be diverted 

 from its present course. The neighbouring isothermals would follow 

 the course of that of 32° with approximate parallelism. The July 

 isothermals, which should traverse the sea that we are now supposing 

 to extend nearly as far east as the Ural Mountains, would be deflected 

 southward as they are at present on approaching the shores of west- 

 ern Europe. It will be observed that the July isothermal of 63°'5 

 intersects the January one of 32° (as I have drawn them for the case 

 previously considered of the absence of the Gulf-stream) at a point 

 very near the extreme western coast of Brittany (art. 11, p. 65). 

 Between this point and the meridian of the Ural Mountains, the Ja- 

 nuary line would lie more to the north and the July one more to the 

 south, by the influence of the extended ocean. The effect, therefore, 

 would be to equalize in a greater degree than at present the summer 



