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 storm area―to escape dangers rather than battle through them as a ship must do.

The choppy days at sea have a counterpart in what fliers call "bumpy" conditions over land. Air is liquid flow and where obstructions occur there will be eddies. For instance, imagine wind blowing directly toward a clump of trees, or coming in sudden contact with a cliff or steep mountain. Water is thrown up when it strikes against a rock and just so is a stream of air broken on the object in its way, and diverted upward in atmospheric gusts which correspond to the spray of the seaside. Encountering such a condition a plane gets a "wallop"―is tossed up and buffeted as it rolls over the wave.

There are bumps, too, from sources other than these land shoals. Areas of cool air and warm disturb the flow of aerial rivers through which the plane moves. The "highs" and "lows" familiar to the meteorologists—the areas of high and low barometric pressure—are forever play-