Winds are caused as a result of differences in temperature between the various layers of the atmosphere. A certain amount of air becomes heated and rises, and as explained before, expands. As the air expands, it becomes lighter, and because it is light it goes upward toward higher regions. It also flows from hot to cold countries. A good illustration of this is the sea breezes. If you have lived around the seashore in the summer time, you will have observed that during the hot part of the day the winds generally blow from the sea toward the land. At night the direction of the wind is reversed, that is, it blows from the land to the sea. Why? Because the land during the day retains its heat, while the water diffuses it. What is the result? The air on the land expands, becomes light. The air over the water being cool, it does not expand, and the result is that it presses toward the land. At night the land loses its heat more rapidly than the water, so that it is not long before the land is cooler than the water, and when this happens, the air over the land, which has become cooler, presses seaward. KINDS OF WINDS =Mountain Breezes=: Caused by the heating and cooling of the hills and valleys. =Avalanche Winds=: Winds that are in front of a landslide, caused by the movement of the snow forcing the air in front of it. [Illustration: Fig. 13 ] [Illustration: Fig. 14 ] [Illustration: Fig. 15 ] [Illustration: Fig. 16 ] [Illustration: Fig. 17 ] =Volcanic Winds=: Due to volcanic eruption, which produces an outrush of air. =A Squall=: Due to the sudden disturbance in temperature. =A Simoon=: A desert wind. VELOCITY OF WIND The wind blows a great deal harder on water than on land, because on land it meets with various obstacles, whereas it has very little friction on the water. THE FORCE OF THE WINDS Wind blowing at 20 miles per hour has a force of 1¼ lbs. Wind blowing at 35 miles per hour has a force of 6 lbs. Wind blowing at 50 miles per hour has a force of 13 lbs. Wind blowing at 75 miles per hour has a force of 28 lbs. Wind blowing at 90 miles per hour has a force of 40 lbs. DAY SIGNALS [Illustration: Fig. 18 ] [Illustration: Fig. 19 ] [Illustration: Fig. 20 ] [Illustration: Fig. 21 ] [Illustration: Fig. 22 ] [Illustration: Fig. 23 ] NIGHT SIGNALS [Illustration: Fig. 19A ] [Illustration: Fig. 20A ] [Illustration: Fig. 21A ] [Illustration: Fig. 22A ] [Illustration: Fig. 23A ] NAME OF WINDS Beaufort’s scale, used in preparation of all Weather Bureau wind forecasts and storm warnings.