70 On the Whirling Action of the 
The whirling motion, however, has not been recognized by 
Prof. Bache, Mr. Espy,* or Prof. Walter R. Johnson,+ in their 
several accounts of the New Brunswick tornado; these writers 
having been led to adopt or favor a theory of astehiling columns 
in the atmosphere, founded on the supposed influence of calorific 
expansion accompanying the condensation of vapor. 
It is remarkable that previous to this period the evidences of 
the rotation or other characteristic action of tornadoes appear not 
to have been duly examined-and recorded, nor even to have re- 
ceived the distinct consideration of scientific observers. We are 
therefore left. to seek out the peculiarities of their action, by ex- 
amining the direction of the prostrations and other effects of the 
wind; and from a careful induction from the effects which are 
thus registered as by the finger of the tornado, we may hope to 
arrive at satisfactory conclusions. 
the erous prostrations of trees and other objects, which 
may be observed in the path of a tornado, be the effects of a vio- 
lent whirlwind, it appears most reasonable to infer that this whirl 
had the common properties which may be observed in all narrow 
and violent vortices, viz. a spirally descending and involuted mo- 
tion of the exterior and lower portions of the vortex, rapidly 
quickened in its gyrations as it approaches toward the centre or 
axis of the whirl, and thence continued (in the case of the whitl- 
wind) spirally upward, but gradually expanding in its spiral 
course by an evolute motion in ascending towards the extreme 
height of the revolving mass. 
If we now contemplate the action of this whirling body, while 
in a state of rapid progression, on the several objects found in dis- 
tinct portions of its path, we may expect to witness effects of 
much complexity, particularly as regards direction ; and, also, 
that amid this apparent complexity, some clue may be obtained 
that will serve to indicate or establish the true character of its 
action. Some of the effects which may be expected or observed, 
will be here considered. 
1. We may expect to find, in the path of the wiiiwiad, strong 
evidence of the inward or vorticular course of the wind at the 
earth’s surface ; the violence of which inward motion is clearly 
- 
* Trans. Amer. Phil. Society, vol. v, New Series. 
t Journ, Academy Nat. Sciences of Philadelphia, vol. vii, part ii. 
