Page:Physical Geography of the Sea and its Meteorology.djvu/466

440 other there is but little land and loss snow. On the polar side of 40° S. especially, if we except the small remnant of this continent that protrudes beyond that parallel in the direction of Cape Horn, there is scarcely an island. All is sea. There the air is never dry; it is always in contact with a vapour-giving surface; consequently, the winds there are loaded with moisture, which, with every change of temperature, is either increased by farther evaporation or diminished by temporary condensation. The propelling power of the winds in the southern hemisiphere resides chiefly in the latent heat of the vapour which they such up from the engirdling sea on the polar side of Capricorn.

824. ''Lieut. Van Gough's Storm and Main Charts.''—The Storm and Rain Charts show that within the trade-wind regions of both hemispheres the calm and rain curves are symmetrical; that in the extra-tropical regions the symmetry is between the calm and fog curves; and also, especially in the southern hemisphere, between the gale and rain curves. Lieutenant Van Gough, of the Dutch Navy, in an interesting paper on the connection between storms near the Cape of Good Hope and the temperature of the sea, presents a storm and rain chart for that region. It is founded on 17,810 observations, made by 500 ships, upon wind and weather, between 14° and 32° E., and 33° and 37° S. By that chart the gale and rain curves are so symmetrical that the phenomena of rains and gales in the extra- tropical seas present themselves suggestively as cause and effect. The general storm and rain charts of the Atlantic Ocean, prepared at the National Observatory, Washington, hold out the same idea. Let us examine, expand, and explain this fact.

825. The "brave west winds" caused by rarefaction in the antarctic regions.—We ascribe the trade-winds to the equatorial calm-belt. But to what shall we ascribe the counter-trades, particularly of the southern hemisphere, which blow with as much regularity towards the pole as the north-east trades of the Atlantic do towards the equator? Shall we say that those winds are drawn towards the south pole by heat, which causes them to expand and ascend in the antarctic regions? It sounds somewhat paradoxical to say that heat causes the winds to blow towards the poles as well as towards the equator; but, after a little explanation, and the passing in review of a few facts and circumstances,