The velocity of the whirling winds in a tornado increase towards the center, and it is because of this that the point of danger is only a small distance from the funnel cloud. The direction of the whirling motion is from right to left. From the appearance of the funnel formed in a tornado, it looks as though the currents were descending from the cloud to the earth, when in reality the currents are ascending. The ascending current draws on the warm and moist air near the surface of the earth for its supply, and this inrush of air in a spiral form into the low pressure core made by the higher whirl constitutes the destructive blast of the tornado. Tornadoes approach rapidly, and it is therefore almost impossible for those who happen to be in their path to escape their violence. A tornado at sea is termed a water spout. RAINFALL You will recall a preceding statement that evaporated humidity turns into water when it becomes cool below a certain point. (See page 14, Effect of the Sun.) A given amount of air will hold a certain amount of moisture. For example, let us assume that a cubic foot of air (see Fig. 11) is saturated, that is, it is holding all the water it will retain. Now if this cubic foot of air is cooled, it will contract, and as a result there will not be enough room to hold both the air and moisture, so the excess moisture will leak out. (See Fig. 12.) The result of this reduction in temperature causes precipitation, simply because the air cannot sustain the water that is in it. Therefor, at any time when moisture in the air has reached the point of saturation and a chilling takes place, due to the air becoming cold, rain follows. This may happen as a result of air rising into higher places or cooler levels, or through its contact with cooler surfaces. WHY WE GET SUCH HEAVY RAINFALLS SOMETIMES AROUND MOUNTAINS The air becomes thoroughly saturated. When air is comparatively warm, it will expand, and this air, which is heavily saturated is brought up by breezes onto the mountain range, which is cold, causing the air to lose its heat and contract and really force the water out of the air. The same principle applies to sea breezes bringing rain. WINDS