LOW BAROMETER OF ANTARCTIC ZONE. 299 



ments of the atmosphere. The experiments of Gay- 

 Lussac, Dalton, and others, have long since proved that 

 the actual effects of the quiet evaporation of water are 

 those here described. It is on this account that Deluc's 

 hypothesis in explanation of the fall of the barometer 

 when the air is moist is now no longer accepted. It 

 has been shown that the observed fall is not due to the 

 moistness of the air, but to increase of temperature. 

 Hot winds bring (in Europe) moist air, and thus moist 

 air and a low barometer are found to be coexistent 

 phenomena. But they are not in the relation of cause 

 and effect. In fact, in New Holland, where hot winds 

 bring dry air, we find the barometer low when the air 

 is dry. 



It follows from what has just been said of the manner 

 in which aqueous vapour associates itself with air, that 

 atmospheric pressure is increased instead of diminished 

 by the process of quiet evaporation, since the weight 

 of the vapour is added to that of the air. Therefore, 

 all things being equal, we should expect to find the 

 barometer higher in the southern or watery hemisphere 

 than in the northern. 



It might seem unnecessary to consider Maury's theory 

 further, but as some doubts may still remain whether 

 some process of the kind conceived by him may not 

 take place, 1 I proceed to consider the efficiency of such 



1 In fact, Sir J. Herschel, in his work on Meteorology, assigns as a 

 cause of the low barometric pressure near the equator, compared with 

 that near the tropics, a process similar to that conceived by Maury, only 

 depending on the excess of heat near the equator. I cannot but agree 



