430 PHYSICAL geoctRaphy of the sea, and its meteorology. 



abundantly to the equatorial calm belts ; tliis would make precipi- 

 tation there more copious, and the additional quantity of beat 

 set free would give additional velocity to the inrusliing trade -winds. 

 Thus it is, as has already been stated, that, parallel for parallel, 

 between 40° or 50" north and south, trans-equatorial seas are cooler 

 than cis-equatorial ; thus it is that icebergs are employed to push 

 forward the -^dnds 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 regulator, with adjustments the most beauti- 

 ful, and compensations the most exquisite, in the grand machinery 

 of the atmosphere. 



832. With this illustration concerning the dynamical force which 

 The antarctic calm thc wiuds derivo, froui thc vapom" taken up in one 



place a region of con- -,., -, , ' xTj. m i 



stant precipitation, climato aud transported to another, we may proceed 

 to sketch those physical featm^es which, being found in the antarctic 

 circle, would be most favom-able to heavy and constant precipitation, 

 and, consequently, to the development of a system of aerial circula- 

 tion peculiarly active, vigorous, and regular for the aqueous hemi- 

 sphere, as the southern in contrast with the northern one may be 

 called. These vapour-bearing winds which brought the rains to 

 Patagonia are — I wish to keep this fact in the reader's mind — the 

 counter-trades (§ 257) of the southern hemisphere. As such they 

 have to perform their romid in the grand system of aerial circula- 

 tion, and as, in every system of aerial cumulation there must be 

 some point or place at wliich motion ceases to be direct and com- 

 mences to be retrograde, so there must be a place somewhere on 

 the sm^face of our planet where these winds cease to go forward, 

 stop, and commence their retm'n to the north ; and that place is, in 

 all probahilitij , within the antarctic regions. Its precise locality 

 has not been determined, but I suppose it to be a band or disc — an 

 area — within the polar cu'cle, which, could it be explored, would be 

 found, like the equatorial calm belt, a place of light airs and calms, 

 of ascending columns of au% — a region of clouds, of variable winds, 

 and constant precipitation. 



833. But, be that as it may, the an- which these vapour-bearing 

 Also of a low bare- winds — vapour-bcaring 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 



