IV. CLIMATE. 



That the Antarctic regions have, till now, remained the 

 least known on the face of the earth is due solely to their 

 inhospitable climate, which precludes the possibility of 

 any human settlements, and compared with which the 

 most northern Arctic regions known to us may be con- 

 sidered as delightful habitations. At first sight it is 

 simply surprising to notice such an enormous difference 

 in the climates of the two Polar regions ; but on con- 

 sidering their external conditions, we speedily arrive at 

 the conclusion that this difference is no more a fortu- 

 itous accident than any other phenomenon in nature, but 

 on the contrary is deeply rooted in general circumstances 

 which are still only partially understood. 



It is well known that solar heat is the primary 

 source of all climatic phenomena, and the mere mathe- 

 matical aspect of its distribution shows that the southern 

 hemisphere is placed at a disadvantage when compared 

 with the northern hemisphere. The fact that at about the 

 time of our winter solstice the earth is in her perihelion, 

 where her angular orbital motion is greatest, brings it 

 about that the sun shines only 179 days in the year 

 vertically over places in the southern hemisphere, but 

 186 days over regions in our northern hemisphere. The 

 southern summer is probably somewhat hotter than the 

 northern summer, in consequence of the greater nearness 

 of the sun ; but, on the other hand, the southern winter 

 is longer, and, because of the greater distance of the sun,. 



colder than the northern winter. 



(228) 



