Page:Physical Geography of the Sea and its Meteorology.djvu/472

446 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 moderate the gale. For, if the water of southern seas were warmer, evaporation would be greater; then the S.E. trade-winds would deliver vapour 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 inrushing 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 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 regulator, with adjustments the most beautiful, and compensations the most exquisite, in the grand machinery of the atmosphere.

832. The antarctic calm place a region of constant precipitation.—With this illustration concerning the dynamical force which the winds derive, from the vapour taken up in one climate and transported to another, we may proceed to sketch those physical features which, being found in the antarctic circle, would be most favourable to heavy and constant precipitation, and, consequently, to the development of a system of aerial circulation peculiarly active, vigorous, and regular for the aqueous hemisphere, 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 round in the grand system of aerial circulation, and as, in every system of aerial circulation there must be some point or place at which motion ceases to be direct and commences to be retrograde, 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 probability, within the antarctic regions. Its