46 Mr. Redfield on the Rotary Action 
prising a length of radius equal to the greatest width of the 
prostrating power on the right of the axis of its path. Now 
Fig. 4. 
@. 
“as ng en enn SEND 
Right boundary of prostration. 
if the tornado be considered as whirling in the manner here 
represented, but without any change of loeation, its action may 
be supposed as concentrically equal on all sides; the motion, 
however, becoming quickened towards the centre in the znverse 
ratio of the successive concentric areas; that is, each particle 
of air as it revolves about the axis, continuing to describe nearly 
equal areas in equal times, in its progress towards the centre, 
where it rises spirally in the direction of discharge; this direc- 
tion being towards the point or area of least atmospheric re- 
sistance or pressure. Thus the course of a single particle, 
horizontally, may be abc def g hi k;—and so on or between 
each of the four involuted lines which constitute the figure. 
For further reference, we may divide this figure by the cross 
lines of arrow heads, into the four quadrants 1, 2, 3, 4. 
We will now consider this whirl as having a@ constant pro- 
gressive motion on the line of the long arrow c¢, ata rate equal 
to one fourth or fifth of its average rotative velocity. It will 
then follow, that as the force of the whirl on the trees and 
