Physical Theory of Secular Changes of Climate. 187 



thick coating of ice "*. On visiting the barrier next year about 

 the same season, he again ran the risk of being frozen in. He 

 states that the surface of the sea presented one unbroken sheet 

 of young ice as far as the eye could discover from the masthead. 



Lieutenant Wilkes, of the American Exploring Expedition, 

 says that the temperature they experienced in the antarctic re- 

 gions surprised him, for they seldom, if ever, had it above 30° 

 even at midday. 



These extraordinarily low temperatures during summer, which 

 we have just been detailing, were due solely to the presence of 

 snow and ice. In South Georgia, Sandwich Land, and some other 

 places which we have noticed, the summers ought to be about 

 as warm as those of England; yet to such an extent is the air 

 cooled by means of floating ice coming from the antarctic regions, 

 and the rays of the sun enfeebled by the dense fogs which pre- 

 vail, that there is actually not heat sufficient even in the very 

 middle of summer to melt the snow lying on the sea-beach. 



We read with astonishment that a country on the latitude of 

 England should in the very middle of summer be covered with 

 snow down to the sea-shore, and the thermometer seldom rising 

 much above the freezing-point. But we do not consider it so 

 surprising that the summer temperature of the polar regions 

 should be low, for we are accustomed to regard a low tempera- 

 ture as the normal condition of things there. We are, however, 

 mistaken if we suppose that the influence of ice on climate is less 

 marked at the poles than at such places as South Georgia or 

 Sandwich Land. 



It is true that a low summer temperature is the normal state 

 of matters in very high latitudes, but it is so only in consequence 

 of the perpetual presence of snow and ice. When we speak of 

 the normal temperature of a place we, of course, as we have 

 already seen, mean the normal temperature under the present 

 condition of things. But were the ice removed from those 

 regions, our present Tables of normal summer temperature 

 would be valueless. These Tables give us the normal June tem- 

 perature while the ice remains, but they do not afford us the 

 least idea as to what that temperature would be were the ice re- 

 moved. The mere removal of the ice, all things else remaining 

 the same, would raise the summer temperature enormously. 

 The actual June temperature of Melville Island, for example, is 

 37°, and Port Franklin, Nova Zembla, 36°*5 ; but were the ice 

 removed from the arctic regions, we should then find that the 

 summer temperature of those places would be about as high 

 as that of England. This will be evident from the following 

 considerations: — 



* Antarctic Regions., vol. i. p. 240. 



