SQQ THE PHYSICAL GEOGRAPHY OF THE SEA. 



that would be set free, in the condensation and congelation in the 

 antarctic regions, of as much vapor as it took to make the Patago- 

 nian rain-fall, if we vary the illustration by supposing this rain-fall 

 of 153.75 inches to extend over an area of 1000 square miles, and 

 that it fell as snow or hail. The latent heat set free among the 

 clouds during these 41 days would have been sufS.cient to raise 

 from the freezing to the boiling point all the water in a lake 1000 

 square miles in area and 83J feet in depth. We now see how 

 the cold of the poles by facilitating precipitation is made to react 

 and develop heat, to expand the air and give force to the winds. 



1018. Thus we obtain another point of view from which we 

 may contemplate, in a new aspect, the icebergs which the antarctic 

 region send forth in such masses and numbers. 



They are a part of the meteorological machinery of our planet. 

 The ofiices which they perform as such are most important, and 

 oh, how exquisite ! While they are in the process of congelation 

 the heat of fluidity is set free, which, whether it be liberated by 

 the freezing of water at the surface of the earth, or of the rain- 

 drop in the sky, helps in either case to give activity and energy 

 to the southern system of circulation by warming and expanding 

 the air at its place of ascent. 



Thus, the water, which, by parting with its heat of liquefaction, 

 has expended its meteorological energy in giving dynamical force 

 to the air, is like the exhausted steam of the engine ; it has exerted 

 its power and become inert. It is, therefore, to be got out of the 

 way. In the grand meteorological engine which drives the wind 

 through his circuits, and tempers it to beast, bird, and plant, this 

 waste water is collected into antarctic icebergs, and borne away by 

 the currents to more genial climes, where the latent heat of fluidity 

 which they dispensed to the air in the frigid zone is restored, and 

 where they are again resolved into water, which, approaching the 

 torrid zone in cooling streams, again joins in the work and helps 

 to cool the air of the trade-winds, to mitigate climate, and moder- 

 ate the gale. For, if the water of southern seas were warmer, evap- 

 oration would be greater ; then the S.E. trade-winds would deliver 

 vapor more abundantly to the equatorial calm belts : this would 

 make precipitation there more copious, and the additional quantity 

 of heat set free would give additional velocity to the in-rushing 

 trade-winds. Thus it is, as has already been stated, that, parallel 



