IGl FIIYSICAL GEOGRAPHY OF THE SEA, AND ITS METEOROLOGY. 



polar side, is clearly indicative of a crossing. Upon no other 

 supposition can we account for the barrenness on one side, the 

 fertility on the other. The following are also links in the chain 

 of facts and circumstances which give strength to the supposition 

 that the rains for the Lena and the Missouri are brought across 

 the calm belt of Cancer by those currents of air which flow thence 

 towards the pole as the prevailing counter-trades or south- 

 westerly winds of the extra-tropical north. We have already 

 seen (§ 353) that, on the north side of this calm zone of Cancer, 

 the prevailing winds on the surface are from this zone towards 

 the pole, and (Plate I., § 215) that these winds return as A B C 

 through the upper regions from the pole ; that, arriving at the 

 calms of Cancer, this upper current, ABC, meets another upper 

 current, S E, from the equator, where they neutralize each other, 

 produce a calm, descend, and come out as surface winds, D E, or 

 the trade-winds ; and as T XJ, or the counter-trades. Now ob- 

 servations have shown that the winds represented by T U are 

 rain winds ; those represented by D E, dry winds ; and it is 

 evident that ABC could not bring any vapours to these calms 

 to serve for T U to make rains of; for the winds represented by 

 ABC have already performed the circuit of surface winds as far 

 as the pole, during which journey they parted with all their 

 moisture, and, returning through the upper regions of the air to 

 the calm belt of Cancer, they arrived there as dry winds. The 

 winds represented by D E are dry winds ; therefore it was sup- 

 posed that these are, for the most part, but a. continuation of the 

 winds ABC. On the other hand, if the winds A B C, after 

 descending, do turn about and become the surface winds T- U, 

 they would first have to remain a long time in contact with the 

 sea, in order to be supplied with vapour enough to feed the gi'eat 

 rivers, and supply the rains for the whole earth between us and 

 the. north pole. In this case, we should have an evaporating 

 region at sea and a rainless region ashore on the north as w^ell as 

 on the south side of this zone of Cancer ; but investigation shows 

 no such region. Hence it was inferred that B C and K S do 

 come out on the surface as represented by Plate I. But what is 

 the agent that should lead them out by such opposite paths ? 

 According to this mode of reasoning, the vapours which supply the 

 rains for T U would be taken up in the south-east trade-wind 

 region by Q, and conveyed thence along the route Q E S to T. 

 And if this mode of reasoning be admitted as plausible — if it be 



