Page:The National geographic magazine (IA nationalgeograph21890nati).pdf/273

 The The next and

Law

209

of Storms.

last plate, entitled,

—

Hurricanes in the North Atlantic. Typical Circulation op the Wind, from Actual Observation, gives a

more complete

still

hurricanes, with

a brief

illustration of the wind-circulation in

discussion of the application of the

Especial attention

8-point rule.

is

called to the statement

made

thereon (referring, of course, to hurricanes in the North Atlantic,

but no doubt true for the entire Northern Hemisphere) that " although the 8-point rule is nearly true when the wind is anywhere from north to south by way of west (that is, generally speaking, in the navigable semicircle), it is liable to be a very poor guide when the wind is from any point in the first or second quadrant."

Also to the following, which is applicable to the Southern Hemisphere by the substitution of "to the left" for "to the right



" Perhaps the best general rule is that the center bears about eight points to the right of the direction from which the low clouds come, or, what is practically the same thing, eight points to the right of the wind at the moment of a sudden shift in a heavy squall after such a shift the wind will remain steady in direction for a time, but the center is meanwhile moving along and the angle of bearing changes until the next shift, wben it goes again to eight points, and so on."

Such diagrams, carefully prepared from complete and

reliable

data, are of far greater practical value to navigators than vol-

umes

they appeal to the eye and will live in long after ideas conveyed by printed words have been

of explanation

memory



forgotten. Finally,

let

us look for a

moment

at

two sketches that

I

have made to give a graphic and I hope not incorrect idea of the cloud formation and the internal structure of a hurricane. In both sketches the vertical scale is of course greatly exaggerated. The first illustrates particularly the great cloud bank (with the

•"

bull's

eye," or clear central space,

shown

in cross-

storm-wave or general elevation of the surface of the ocean caused by the spirally in-blowing winds and low barometric pressure (the cause, oftentimes, of fearful floods along low-lying coasts); and the probable, or possible, circulation of theupper atmosphere over the whirl, together with the direct and reflected rays of a vertical sun as they pottr into the central calm. The second sketch is to aid a clear mental conception of section); the