[Illustration: FIGHTING FROST IN AN ORCHARD--NIGHT.] [Illustration: FIGHTING FROST IN AN ORCHARD--DAWN. The pall of smoke prevents evaporation and keeps the air near the ground from freezing temperatures. _Copyright by J. Cecil Alter, U.S. Weather Bureau, Cheyenne, Wyo._] [Illustration: BUCKING A SNOW DRIFT.] [Illustration: CLEAR THE WAY! Even an avalanche cannot stop Man, backed with the resources of modern snow-fighting machinery. _Courtesy of Northern Pacific Railway Co._] [Illustration: MEASURING THE BLIZZARD'S RAGE. Shielded snow gauge in the Northwest to register the amount of snow-fall. _Courtesy of U. S. Weather Bureau._] [Illustration: SIGNALS ON DELAWARE BREAKWATER. _Courtesy of Geo. S. Bliss, U.S. Weather Bureau, Philadelphia, Pa._] [Illustration: SIGNAL TOWER FOR STORM WARNINGS. Flags used by day, lanterns by night. _Courtesy of U.S. Weather Bureau._] [Illustration: THERMOMETERS AND RAIN-GAUGE. Instruments in shelter, as supplied to each co-operative observer. _Courtesy of the U.S. Weather Bureau._] [Illustration: PENCIL DRAWINGS OF TORNADO IN DAKOTA. For many years this was an authoritative series of pictures, and shows:--(A) Tornado becoming a waterspout;--(B) Tornado wrecking a farmhouse and barn, nothing but fragmentary timbers being thrown out;--(C) Tornado funnel rising from the ground;--(D) Successive funnel formations, with a second whirl reaching ground and sucking up a pillar of dust. _Copyright by Sam W. Glenn, Courtesy of U. S. Signal Service._] [Illustration: TRUE TORNADO FORMING IN ADVANCE OF A DUST WHIRL. _Courtesy of U.S. Weather Bureau._] [Illustration: TORNADO DROPPING TOWARDS GROUND. _Courtesy of T. B. Jennings, U.S. Weather Bureau, Topeka, Kans._] [Illustration: TORNADO WRECKING A FARM. Whirl had been in action for ten minutes when photo was taken. _Courtesy of T. B. Jennings, U.S. Weather Bureau, Topeka, Kans._] [Illustration: TORNADO WHIRLING SIDEWISE. The swaying motion of the funnel cloud makes the path of escape uncertain. _Courtesy of U.S. Weather Bureau._] [Illustration: GALVESTON CAUSEWAY BEFORE THE HURRICANE.] [Illustration: GALVESTON CAUSEWAY AFTER THE HURRICANE. The Sea-Wall saved the greater part of Galveston in the hurricane of 1915, but the Causeway was exposed to the full fury of wind and water. _Courtesy of I. R. Tannehill, U. S. Weather Bureau, Galveston, Tex._] [Illustration: SHOT FROM THE GUN OF A HURRICANE. Thin strips of weather-boarding driven through a porch post, a marvellous example of the force of a hundred-mile-an-hour wind. Straws have been driven into brick walls in similar fashion. (Upper photo taken from across the street; lower photo at close range.) _Courtesy of I. R. Tannehill, U. S. Weather Bureau, Galveston, Tex._] [Illustration: 1. ZEPHYR] [Illustration: 2. LIGHT BREEZE] [Illustration: 3. FRESH BREEZE] [Illustration: 4. MODERATE WIND] [Illustration: 5. STRONG WIND] [Illustration: 6. GALE]