. A complete geography. omes expanded and light. The heavier air to the north and south flows in, pushing the .obxhpoJM light air away and pro- Fig. 293. ducing winds, known as Diagram to show, by arrows, the movement of the greater the trade winds (Fig. winds of the earth. 293), which begin in the temperate zones, hundreds of miles away. Since the heated air must escape somewhere, it rises far abovethe surface, and then moves back in the same direction from whichit came, forming the return trades or anti-trade winds (Fig. 293).The atmosphere extends many miles above the earth, so that^there i
. A complete geography. omes expanded and light. The heavier air to the north and south flows in, pushing the .obxhpoJM light air away and pro- Fig. 293. ducing winds, known as Diagram to show, by arrows, the movement of the greater the trade winds (Fig. winds of the earth. 293), which begin in the temperate zones, hundreds of miles away. Since the heated air must escape somewhere, it rises far abovethe surface, and then moves back in the same direction from whichit came, forming the return trades or anti-trade winds (Fig. 293).The atmosphere extends many miles above the earth, so that^there isplenty of room for two winds blowing in opposite directions, oneabove the other. In Cuba, the Caribbean Sea, and elsewhere, where the trade windsat the surface are blowing toward the southwest, one notices that theclouds far up in the sky are steadily borne in the opposite direction bythe anti-trades. Also, when volcanoes in Central America have been ineruption, the ashes that were blown out from them have been carried. 260 GENERAL GEOGRAPHY hundreds of miles in a direction opposite to tliat of the prevailing tradewinds at the surface. Being cooled on account of its great height, the air of the anti-trades slowly settles, some of it coming to the surface at about athird of the distance to the poles. There it spreads out, a part con-tinuing on toward the poles, a part returning to the equator as thetrade winds (Fig. 293). As you see, the correspondence between these currents in theatmosphere and those in the room is quite close. In both cases airmoves in toward a heated place, then up, then outward and down,and once more inward toward the heated part. Make a drawing toillustrate these/oitr directions of movement of the air. Effect of Rotation. — There are differences, however, and one of themis especially important. In the case of the room, the currents movedirecJhj toward the stove; then, after rising, directly away from it. If theearth stood perfectly still, the trade winds
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