TRANSACTIONS OF THE SECTIONS. 



47 



the winds at sea, are to and fro between the Equator and the Poles, all these obser- 

 vations were arranged in two groups for each belt, and classed either as winds with 

 northing, or as winds with southing, in them, as per Table, showing the average 

 annual duration in days of winds. 



It thus appears that we have, as we already well knew, in each hemisphere a 

 medial belt — a barometric ridge in the air — from which the prevailing direction ol the 

 wind on one side is towards the Equator, and from the other towards the Pole. In 

 the southern hemisphere this ridge is sharp, being included between the parallels of 

 35° and 40° ; in the northern hemisphere, however, it seems to be less sharply de- 

 fined, for the debateable ground, or bolt, within which neither wind app<ars to have 

 a very marked ascendency as to prevalence, extends from lat. 25° to 50° N. 



Proceeding from these belts towards the Equator, equatorial-bound winds become 

 more and more prevalent; or if we proceed towards the Pole, the polar-bound winds 

 become more and more prevalent, — thus indicating the existence both near the 

 Equator and in the polar regions of a permanent degree of aerial rarefaction suf- 

 ficient to produce an indraught from a medial line or belt towards each. 



To ascertain the degree of rarefaction about the Poles, as far as the observations on 

 the barometer at sea would indicate a result, the Barometric Curve (Plate II.) was 

 constructed from the data expressed in this Table, showing 



It would seem from this curve, which by its regularity shows the observations at 



