house 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]

[Illustration: 7. FULL GALE]

[Illustration: 8. STORM]

[Illustration: 9. HURRICANE

SCALE OF WINDS ILLUSTRATED BY REDUCTION OF SAIL ON AMERICAN CLIPPER
SHIPS.

_Note._-- This is a combined scale with average wind velocities as
follows:--(0) CALM;--(1) 2 miles an hour;--(2) 7 miles an hour;--(3) 11
miles an hour;--(4) 16 miles an hour;--(5) 22 miles an hour;--(6) 27
miles an hour;--(7) 32 miles an hour;--(8) 45 miles an hour;--(9) 60
miles an hour or more.]

[Illustration: BRANCH LIGHTNING.

_Copyright by H. E. Clark, Indianapolis. Courtesy of U.S. Weather
Bureau._]

[Illustration: MULTIPLE FLASH.

_Courtesy of General Electric Co., Schenectady, N. Y._]