THE ANTARCTIC REGIONS AND THEIR CLIMATOLOGY. 



457 



pared with those which rule at sea. There is barely a resemblance 

 between this profile of the atmosphere 

 over the land and the profile of it (Plate 

 XVI.) over the sea, so different are these 

 influences. The irregularities over the 

 land are chiefly owing to the difference in 

 the amount of precipitation at one station 

 as compared with the amount at another. 

 Those islands, as the Sandwich and Society, 

 which are so situated as to bring down a 

 heavy precipitation, seem to serve as chim- 

 neys to the atmosphere. The latent heat 

 which is liberated by the vopour they 

 condense has the effect of bringing down 

 the barometer, and of causing, during the 

 rainy season, an indraught thitherward 

 from many miles at sea. Such is the rare- 

 faction produced by the liberation of this 

 heat, that its effects are, as the pilot 

 charts show, felt and confessed by the 

 winds at the distance out to sea of more 

 than a thousand miles from the Sandwich 

 Islands. Thus the land and the islands 

 give us in the circulation of the atmo- 

 sphere systems within system. In the 

 Mississippi and all great rivers, the general 

 movement of the waters, notwithstanding 

 the eddies and the whirlpools, is down 

 stream with the current. So with the 

 atmosphere : its general movements are 

 indicated by observations at sea ; its 

 eddies and whirlpools are created by the 

 mountains, and the islands, and other in- 

 equalities, which obstruct its flow in the 

 regular channels. The mean reading of 

 the barometer when the rainy season in 

 India is at its height is 0*4 inch less than 

 it is in the midst of the dry. 



860. Agreement of observations at sea. — 

 The diagram (Plate XVI.) shows the ob- 

 servations in the southern hemisphere to 



bo so accordant, and 



