344 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 

 Bakometic Table. 

 3Iean Height of the Barometer as observed between 



lack tliat uniformity wliicli larger numbers would doubtless give. 

 They show, however, most satisfactorily, that a low barometer is not 

 peculiar to Cape Horn regions alone ; they show that it is common to 

 all high southern latitudes ; and other observations (§ 362) show 

 that it is peculiar to these and not to northern latitudes. Project- 

 ing on a diagram A, with parallels of latitude and the barometric 

 scale as ordinates and abscissae, a cmwe S, which will best re- 

 present the observations (§ 670), and continuing it to the south 

 pole — also projecting another ciuwe N, which mil best represent 

 the observations (§ 362) on the polar side of 40^ N., and con- 

 tinuing it to the north pole — we discover that if the barometric 

 pressure in polar latitudes continue to decrease for the unknown 

 as it does for the known regions, the mean height of the baro- 

 meter would be at the north pole about 29.6, at the south about 28 

 inches. These lines, N and S, represent what may be called the 

 harometric descent of the counter- trades. 



672. The rarefaction of the air in the polar calms is, as we have 

 The "brave west secii (§ 667), Sufficient to create an indraught all 

 mSric d^-scent. ^ °" aroiuid to the distance of fifty degTees of latitude 

 from the south pole ; also (§ 662) the rarefaction in the belt of 

 equatorial calms is sufficient to extend mth its influence no farther 

 than thirty degrees of latitude. The fact also favours the idea sug- 

 gested by the diagram (§ 671), that the mean height of the baro- 

 meter in the polar cahns is very much less than it is hi the equa- 

 torial. Moreover, the counter trades of the southern hemisphere 

 are very much stronger (§ 626) than the counter trades of the 



