Page:Physical Geography of the Sea and its Meteorology.djvu/386

360 to extend with its influence no farther than thirty degrees of latitude. The fact also favours the idea suggested by the diagram (§ 071), that the mean height of the barometer in the polar calms is very much less than it is in the equatorial. Moreover, the counter trades of the southern hemisphere are very much stronger (§ 026) than the counter trades of the other. They are also stronger than the trade-winds of either; these facts likewise favour the idea of a greater exhaustion of air in the antarctic than in the arctic calm place; and it is manifest that actual observations also, as far as they go, indicate such to be the case. In other words, "the brave west winds" of the southern hemisphere have the greatest "barometric descent," and should therefore be, as they are, the strongest of the four winds.

673. Study of the monsoons affords farther information touching the calm belts.—Farther information may be gained upon the subject of high and low barometers, of the "barometric declivity of winds," and of the meteorological influence of diminished atmospheric pressure by studying the calm belts in connection with the monsoons.

674. The south-east winds of the Atlantic.—Before, however, we proceed to these, let us take a hasty glance at the winds in certain other parts of the ocean. The winds which most prevail on the polar side of the calm belt of Cancer, and as far as 50° N. in the Atlantic, are the west wands. "Wind and weather in this part of the ocean," says Jansen, "are very unreliable and changeable; nevertheless, in the summer months, we find permanent north winds along the coast of Portugal. These north winds are worthy of attention, the more so from the fact that they occur simultaneously with the African monsoon, and because we then find northerly winds also in the Mediterranean, and in the Red Sea, and farther eastward to the north of the Indian monsoon. When, between the months of May and November, during which the African monsoon prevails, the Dutch ships, which have lingered in the calm belt of Cancer run with the north-east trade, and direct their course for the Cape Verde Islands, then it seems as if they were in another world. The sombre skies and changeable—alternately chilly and sultry—weather of our latitudes are replaced by a regular temperature and good settled weather. Each one rejoices in the glorious heavens, in which none save the little trade-clouds are to be seen—which clouds in the