ANNIVERSARY ADDRESS OF THE PRESIDENT. 1x1 



In the case in which the Gulf-stream is supposed to exist, but its 

 progress into the North Sea to be arrested by a continuous barrier of 

 land, I have shown that the winter temperature of the coast of Ice- 

 land would probably be increased 6° or 7° F., and that the January 

 isothermal would probably run nearly north and south from Iceland 

 to the latitude of central France. You will recollect that a former 

 littoral or sub-littoral communication between the western coasts of 

 Europe and the eastern coasts of America is rendered probable by a 

 certain community of specific forms in those localities. My object, 

 in considering the effect of the configuration of land above-mentioned, 

 is to determine how far it might afford this littoral communication 

 with a temperature of the ocean sufficiently high to admit of the dis- 

 semination along it of the species alluded to. 



The next case is that in which the basin of the Atlantic should 

 be converted into dry land, so as to unite the old and new continents. 

 This would give to our own region the extreme continental climate of 

 northern and central Asia. According to my estimate, we should 

 then have for Snowdon, 



Temperature of January. ... 7° F. "I j..rp ^qo r 



July 66°'5 J^'**- ^'^ '^' 



Mean annual temperature . . 29°* 75 



The summer temperature would be increased 5°'5 F., but the winter 

 temperature would be reduced 45°, and the mean annual tempera- 

 ture 20°. 



In discussing the fourth case, in which the Gulf-stream is not sup- 

 posed to exist on our own shores, and a great part of Europe is assumed 

 to be submerged beneath the ocean, I have shown that the mean, 

 annual temperature would be very nearly the same in western Europe 

 and in the latitude of Snowdon, as in the case above-considered of 

 simply the absence of the Gulf-stream. The conditions under which 

 the Welsh and Irish mountains would be placed, supposing them 

 extant above the sea while the neighbouring region was submerged, 

 would be very similar to the existing conditions of the Falkland Is- 

 lands and the island of S. Georgia ; and a comparison with these 

 islands leads me to conclude that the estimate above-given of the 

 mean annual temperature of Snowdon (42° F.) is two or three de- 

 grees too high. I have considered 39° or 40° F. to be a nearer 

 estimate. In fact, a great part of the misconception which has existed 

 respecting the possible past temperature of this region, has arisen 

 from' our regarding its present temperature as the normal temperature 

 for our own latitude, and that of places like the island of S. Georgia, 

 in corresponding south latitudes, as the abnormal temperature ; 

 whereas the exact reverse of this is the actual case. 



Having determined the positions of the isothermal lines for any 

 particular hypothetical case, we can determine, for that case, the 

 mean annual temperature at any assigned place. The object which 

 I have next proposed to myself in this paper is more especially to 

 determine the conditions under which glaciers would exist in those 

 parts of western Europe where traces of their former existence have 



