4:48 THE PHYSICAL GEOGRAPHY OF THE SEA. 



of the Cape of Good Hope and Melbourne, the mean barometric 

 pressure on the polar side of 42° S. has been shown by Lieuten- 

 ant Van Gogh, of the Dutch Navy, to be 0.33 inch less than it is 

 in the trade-winds. The mean pressure in this part of the South 

 Indian Ocean is, under winds with easting in them, 29.8 inches ; 

 ditto, under winds with westing, 29.6 inches. Plate I. shows a sup- 

 posed mean pressure in the polar calms of not more than 28.75 

 inches. 



834. To what, if not to the effects of the condensation of vapor 

 Aqueous vapor the bomc by thosG surchargcd winds, and to the im- 

 causeofboth. mcnsc prccipitatlon in the austral regions, shall 

 we ascribe this diminution of the atmospherical pressure in high 

 south latitudes ? It is not so in high north latitudes, except about 

 tlie Aleutian Islands of the Pacific, where the sea to windward is 

 also wide, and where precipitation is frequent, but not so heavy. 

 The steady flow of "brave" winds toward the south would seem 

 to call for a- combination of physical conditions about their stop- 

 ping-place exceedingly favorable to rapid, and heavy, and con- 

 stant precipitation. The rain-fall at Cherraponjie and on the 

 slopes of the Patagonian Andes reminds us what those conditions 

 are. There mountain masses seem to perform in the chambers 

 of the upper air the ofi&ce which the jet of cold water does for the 

 exhausted steam in the condenser of the engine. The presence 

 of land, not water, about this south polar stopping-place is there- 

 fore suggested; for the sea is not so favorable as the mountains 

 are for aqueous condensation. 



835. By the terms in which our proposition has been stated, and 

 The topographical fea- thc mauucr iu which the demonstration has been 



tures of the antarctic ^ _ ^ . . . p 



bands. conducted, the presence m the antarctic regions oi 



land in large masses is called for ; and if we imagine this land to 

 be relieved by high mountains and lofty peaks, we shall have in 

 the antarctic continent a most active and powerful condenser. If, 

 again, we tax imagination a little farther, we may, without trans- 

 cending the limits of legitimate speculation, invest that unexplored 

 land with numerous and active volcanoes. If we suppose this also 

 to be the case, then we certainly shall be at no loss for sources of 

 dynamical force suf&cient to give that freshness and vigor to the 

 atmospherical circulation which observations have abundantly 

 shown to be peculiar to the southern hemisphere. Neither under 



