LOW BAROMETER OF ANTARCTIC ZONE. 297 



'enough, and seems further to coincide with many well- 

 known phenomena. The theory supposes that over a 

 wide zone of the southern hemisphere aqueous vapour 

 is continually rising ; that as it rises it displaces in 

 part the heavier air over these regions; and that 

 equilibrium being thus disturbed, the excess of air flows 

 off continually towards the- equator. Now we know 

 that the prevailing surface-winds over that zone of the 

 southern hemisphere in which the barometer exhibits 

 the peculiarity we are considering, blow from the 

 equator ; that is, they tend to sweep the lower strata of 

 the atmosphere towards the south pole. They therefore 

 tend to increase the quantity of humid air in high 

 southern latitudes. We know also that the prevailing 

 upper currents over the southern zone we are considering 

 blow towards the equator. They tend, therefore, to 

 carry the drier portion of the air towards the equator. 

 All this seems in accordance with Maury's theory, and 

 indeed if the prevailing upper and lower currents flowed 

 in directions contrary to those indicated, the theory 

 would fall at once. 



Again, although we find no evidence in barometric 

 pressure over the south tropical zone of that increase 

 which Maury's theory would lead us to expect (since 

 the surplus air is carried first to this zone), yet it might 

 be argued that the surplus is so distributed as to appear 

 in another way. It is evident that if the atmospheric 

 envelope normally appertaining to the southern hemi- 

 sphere were, through the effects of the causes assigned 

 by Maury, increased in extent, this increase might show 



