458 niYSIOAL GEOGRAniY OF THE SEA, AND ITS METEOROLOGY. 



the curve itself so regular, tliat we feel no hesitation about pro- 

 jecting this curve into the unexplored spaces of the south, 

 and asserting, with all the boldness consistent with the true 

 spirit of philosophical deduction, that, whether the actual 

 barometric pressure at the south pole be as low as 28.14 or not, 

 it is nevertheless very much lower in the antarctic than in the 

 arctic regions. 



861. The question ivhy tlie barometer should stand lower about the 

 south than the north pole considered. — The question now arises, 

 Whence this unequal distribution of atmosphere between the two 

 hemispheres, and why should the mean height of the barometer 

 in circumpolar regions be so much less for the austral than for 

 the boreal ? No one, it is submitted, will attempt to account for 

 this difference by reason of any displacement of the geometrical 

 centre of the earth with regard to its centre of attraction, in 

 consequence of the great continental masses of the northern 

 hemisphere ; neither can it be ascribed to any difference in the 

 forces of gravitation arising from the oblateness of our globe; 

 neither can it be accounted for by the effects of diurnal rotation 

 after the Hallej'an theory : that would create as low a barometer 

 at one pole as the other. The air, in its motions to the east and 

 in its motions to the west, is in equipoise between the parallels 

 of 35° and 40° N., 25° and 30° S. There is near each pole and 

 about the equator a place of permanently low barometer. The 

 air from all sides is continually seeking to restore the equilibrium 

 by rushing into those places of rarefaction and reduced pressure ; 

 consequently there ought to be between each pole and the equator 

 a place of high barometer from which the air on one side flows 

 towards the equator, on the other towards the pole. Observation 

 (p. 455) shows this high place to be between the parallels of 25° 

 and 40° in the north, and of 20° and 30° in the southern hemi- 

 sphere : thus the barometer as well as the winds, Plate XV., are 

 both indicative of a greater degree of rarefaction about the south 

 than about the north pole. Were there no friction, and were the 

 atmosphere ordained to move without resistance, the air from 

 these null belts would carry with it to the polar calms the easterly 

 motion which it had acquired from the earth in its motion around 

 its axis at these null belts. Were this motion so impressed, the 

 wind would arrive, rushing with an hourly velocity about the 

 polar calm places of 700 miles in the arctic, and 800 in the 

 antarctic. Such a velocity would impart a centrifugal force 



