which in turn produces commotion in the air below. But this is digressive. Therefore let us take up the broken thread, and suppose, merely for illustration, such a rain-fall as King and Fitzroy encountered in Patagonia to have taken place under the supposed cloud region of the antarctic circle, and to have been hail or snow instead of rain, then the total amount of caloric set free among the clouds, in those 41 days of such a flood, would be enough to raise from freezing to boiling six and a half times as much water as fell. But if the supposed antarctic precipitation come down in the shape of rain, then the heat set free would be sufficient only to raise from freezing to boiling about of as much water as the flood brought down. We shall have, perhaps, a better idea of the amount of heat that would be set free in the condensation and congelation in the antarctic regions of as much vapour as it took to make the Patagonian 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 sufficient to raise from the freezing to the boiling point all the water in a lake 1000 square miles in area and 83i feet in depth. The unknown area of the antarctic is eight millions of square miles. 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.
831. Offices of icebergs in the meteorological machinery.—Thus we obtain another point of view from which we may contemplate, in a new aspect, the icebergs which the antarctic regions send forth in such masses and numbers. They are a part of the meteorological machinery of our planet. The offices 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
