454 



THE PHYSICAL GEOGRAPHY OF THE SEA. 



liemispliere hold the mastery from 85° S. to 10° K ; i. e., they pre- 

 vail over a belt 45° in breadth, while the others cover a space 

 not half so broad. This table, moreover, shows that the debat- 

 able ground between the winds, or what may be called the nidi 

 belt, in this general movement from poles toward the equator, and 

 from equator toward the poles, is, in the northern hemisphere, 

 between the parallels of 25° and 50°. In the southern the field 

 of battle is narrowed down to a single belt (between 85° and 

 40°) ; here the two winds exactly counterbalance each other. 

 As one proceeds from this medial belt, the winds increase belt 

 for belt very nesirlj pari passu ; on the polar side, the polar winds 

 — on the equatorial, the equatorial winds, gaining more and more 

 in days of annual duration, and more and more in average veloci- 

 ty each. 



858. The fact that the influence of the polar indraught upon 

 Extent of the polar ^^ wiuds should cxtcud from the antarctic to 40° 

 indraught. g_^ whilc that from the arctic is so feeble as scarce- 



ly to be felt in 50° N., is indicative enough as to difference in de- 

 gree of aerial rarefaction over the two regions. The significance 

 of this fact is enhanced by the " brave west winds," which, being 

 bound to the place of greatest rarefaction, rush more violently 

 along to their destination than do the counter-trades of the north- 

 ern hemisphere. Why should these polar-bound winds of the two 

 hemispheres differ so much in strength and prevalence, unless there 

 be a much more abundant supply of caloric, and, consequently, a 

 higher degree of rarefaction, at one pole than the other? 



