54 THE OCEAN WORLD. 



while that from the Arctic is so feeble as scarcely to be felt in 50 

 north, is indication enough as to the difference in degree of aerial 

 rarefaction over the two regions. The significance of the fact is 

 enhanced by the consideration that the * brave west winds/ which 

 are bound to the place of greatest rarefaction, rush more violently 

 and constantly along to their destination than do the counter trades 

 of the northern hemisphere. Why should these polar-bound winds 

 differ so much in strength and prevalence, unless there be a much 

 more abundant supply of caloric, and, consequently, a higher degree 

 of rarefaction, at one pole than at the other ? " 



That this is the case is confirmed by all the known barometrical 

 observations, which are very much lower in th^ Antarctic than in the 

 Arctic, and Dr. Maury thinks this is doubtless due to the excess in 

 the Antarctic regions of aqueous vapour and of latent heat. 



" There is," he writes, " rarefaction in the Arctic regions. The 

 winds show it, the barometer attests it, and the fact is consistent 

 with the Russian theory of a Polynia in polar waters. Within the 

 Antarctic Circle, on the contrary, the winds bring air which has come 

 over the water for the distance of hundreds of leagues all around ; 

 consequently, a large portion of atmospheric air is driven away from 

 the austral regions by the force of vapour." 





