Mr. Redfield on the Tornado of June 19, 1835. 21 



fluence of calorific expansion accompanying the condensa- 

 tion of vapour. 



It is remarkable that up to this period the evidences of the 

 rotation, or other characteristic action of tornadoes, appear 

 not to have been recorded, nor to have received the distinct 

 consideration of scientific observers. We are, therefore, left 

 to seek out the peculiarities of their action, by examining 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. 



If the numerous prostrations of trees and other objects, 

 which may be observed in the path of a tornado, be the 

 effects of a violent whirlwind, it appears most reasonable to 

 infer that this whirl had the common property which may 

 be observed in all narrow and violent vortices, viz. a spirallij 

 involute motion, quickened in its gyrations as it approaches 

 toward the centre or axis of the whirl, and there continued 

 (in the case of the whirlwind) spirally upward, but gradually 

 expanding again in its spiral course 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 distinct portions of its path, we may expect to wit- 

 ness effects of much complexity, particularly as regards the 

 lines of direction; and, also, that amid this apparent com- 

 plexity 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 whirlwind, 

 strong evidence of the inward or vorticular course of the 

 wind: the violence of which inward motion is clearly indi- 

 cated by the force with which various objects, often of much 

 weight, are carried spirally upward about the axis of the re- 

 volving body. 



Now the effects of this inward vorticular motion at the 

 surface of the ground, are clearly manifested in the cases be- 

 fore us; and are also well illustrated by Prof Bache in his 

 paper on this tornado, although referred by him to a difierent 

 action *. 



2. As the effects observed at various points in the track 

 were produced at different moments of time and by forces 

 acting in dilfereut directions, as well as of various intensities, 



• Transactions of American Piiilosophical Society, vol. v. 



