~ 
On the Spirality of Whirlwinds. 23 
the axial area of the storm, and there was not any accumulation 
beyond its active verge, as ave shown in describing the 
condition of the surrounding area of 400 miles in diameter 
through which the tornado progressed. 
Of course the same objections apply to Mr. Espy’s theory: he 
admits that a tornado may very greatly depress the barometer ; 
and “if it should depress it more than 3 inches” then, he says, 
that something more is necessary than is provided for in his the- 
ory,—*‘‘ perhaps electricity.” Itis not a little remarkable that 
when Mr. Espy presented his storm views to the British Associ- 
ation, Sir John Herschel observed, that if an ascensional column 
be the cause of storms, the barometer ought to rise in the centre of 
the storm or column ; a fact which the observation of what actu- 
ally occurs during the passage of a tornado has now verified ; 
for whether the storm progress in the form of an ascensional 
column, or of a cyclone, the facts I have advanced. prove that 
the barometer does rise tin its centre. 
ART, VI—On the Spirality of Motion in Whirlwinds and Tor- 
nadoes ; by W. C. REDFIELD. 
Read before the American Association at Albany, Aug. 26, 1856. 
aggregated spiral movement, around a smaller axial 
1. An 
: constitutes the essential portion of whirlwinds and torna- 
- does, 
i I 
Ward portion of the whirlwind the tendency of this movement 
* obliquely downwards, when the axis is vertical ; but in the in- 
; descending m t, ina metric whirlwind, is that of 
an involuted or closing apieat’ while the course of the interior 
ascending movement of rotation is that of an evolved or opening 
Spiral. Hence, the horizontal areasof the higher portions of the 
whirl exceed greatly those of its lower portions. 
4. The area of the ascending spiral movement in the vortex, 
88 it leaves the earth’s surface, is by far the portion of 
3. Owin p f 
apr oaching the earth’s surface, the normal course of the gradu- 
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