"This gives three belts of weather in the tropical and sub-tropical zones. The first of these is a light up-flowing east wind on or near the equator--it shifts a little to the north or south with the change of the seasons; a belt of heavy rains and calm, the rains being due to the warm, moist, uprising air cooling by expansion so that the moisture is condensed--this region is known to sailors as the 'doldrums' and many a sailing-vessel has been held for weeks there, without enough wind to carry her the few miles necessary to get into the next belt of winds; outside this, come the downflowing easterly currents, known as the trade winds, which form a belt between the tropics and the temperate zones. Beyond this--to the north and south of the tropical zones--come the prevailing belts of strong west winds, which stretch almost to the Poles. "The United States is in this west-wind zone and the strength and regularity of the eastward movement of the weather is because both the winds of the surface and of the upper air blow in the same direction. Naturally, the same conditions are repeated on the other side of the equator. In the southern hemisphere the land masses are not so large and the regularity of the winds is less disturbed. There, the west winds are so strong that certain latitudes are known as the 'roaring forties.' These 'forties' correspond in latitude to the northern third of the United States. Chicago and New York are both in the 'roaring forties' of the northern hemisphere." "The way you tell it, it sounds all right," the farmer objected, "but from my experience, winds blow from all over the place." "Locally, perhaps, they seem to," the weather expert responded, "but if you watched them closely, you'd find that about seventy per cent of the winds come from a westerly direction." "They do here, for a fact," put in Tom, who, as official wind-measurer of the League, had been following the explanation with the keenest attention. "I've noticed that in my kite-flying. The winds are from the southwest or from the northwest nearly all the time." "You mean both in summer and winter?" "Yes," answered Tom, "they're more from the northwest in winter, I think, but they're generally westerly." "If the winds are due to the position of the equator and the poles," the old farmer said shrewdly, "I don't see why summer and winter ought to make any difference."