TRADE-WINDS OF THE SOUTHERN HEMISPHERE. 357 



for parallel, trans-equatorial seas are cooler than cis-eqiiatorial ; 

 thus it is that icebergs are employed to push forward the winds in 

 the Polar regions, to hold them back in the equatorial ; and thus 

 it is that, in contemplating the machinery of the air, we perceive 

 how icebergs are "coupled on," and made to perform the work of a 

 regulator, with adjustments the most beautiful, and compensations 

 the most exquisite, in the grand machinery of the atmosphere. 



1019. With this illustration concerning the dynamical force 

 which the winds derive from the vapor taken up in one climate 

 and transported to another, we may proceed to sketch those phys- 

 ical features which, being found in the antartic circle, would be 

 most favorable to heavy and constant precipitation, and, conse- 

 quently, to the development of a system of aerial circulation pe- 

 culiarly active, vigorous, and regular for the aqueous hemisphere, 

 as the southern in contrast with the northern one may be called. 



These vapor-bearing winds which brought the rains to Patago- 

 nia are — I wish to keep this fact in the reader's mind — the coun- 

 ter-trades of the southern hemisphere. As such they have to per- 

 form their round in the grand system of aerial circulation, and as, 

 in every system of circulation there must be some point or place 

 at which motion ceases to be direct and commences to be retro- 

 grade, so there must be a place somewhere on the surface of our 

 planet where these winds cease to go forward, stop, and commence 

 their return to the north ; and that place is, in all probahility^ within 

 the antarctic regions. Its precise locality has not been determined, 

 but I suppose it to be a band or disk within the polar circle, which, 

 could it be explored, would be found, like the equatorial calm 

 belts, a place of light airs and calms, of ascending columns of air, 

 a region of clouds and of constant precipitation. 



But, be that as it may, the air which these vapor-bearing winds 

 — vapor-bearing because they blow over such an immense tract 

 of ocean — pour into this stopping-place has to ascend and flow off 

 as an upper current, to make room for that which is continually 

 flowing in below. In ascending it expands and grows cool, and, 

 as it grows cool, condensation of its vapor commences; with this 

 vast quantities of latent heat, which converted the water out at 

 sea into vapor for these winds, are set free in the upper air. There 

 it reacts by warming the ascending columns, causing them still far- 

 ther to expand, and so to rise higher and higher. 



