376 JFIiirlwinds excited by Fires. 



2. The foregoing results can be accounted for, only by a vio- 

 lent vortical action, steadily maintained. This appears too 

 plain to need illustration. 



3. The origin of the rotative action and its continuance for 

 a considerable period, in the circuit of conflagi'ation, appear to 

 be chiefly owing to the circular outline of the several fires, and 

 to the absence of a disturbing horizontal current. When, how- 

 ever, the principal seat of the vortical action is found in the 

 body of an elevated current of atmosphere, we then find that 

 the progressive action of the foot of the whirling column upon 

 the earth's surface, and the resistance which is also offered to 

 its progress by an inferior cross current, are not sufiicient to 

 break up, or sensibly impede, the regular action and progress 

 of a poAverful vortex. This was strikingly manifested in the 

 tornado which passed through the city of New Bnmswick, in 

 New Jersey, in June 1835. 



4. Th e ascending power of the vortical column or wh irlwind is, 

 in these cases, strongly exhibited. We observe, that the heated 

 air from large fires, or even from the most powerful furnaces, 

 ejected in a column at the heat of melted iron, Avill ascend only 

 to a comparatively short distance from the earth ; the ascend- 

 ing force being lost in the counter-movements and convolu- 

 tions with the adjacent colder air, and the combined product 

 soon spreads off" in a horizontal direction. But the spire of a 

 columnar vortex, exhibits a penetrating and ascending power 

 which far exceeds, both in its intensity and the extent of its 

 action, any other ascending movement that we witness in the 

 atmosphere. This effect appears to be owing to the spiral 

 motion of the column, which presses onward in the direction of 

 its axis, until it reaches a limit of elevation which Ls yet un- 

 known. Even the ring vortex which is sometimes seen to form 

 at the muzzles of cannon or the ejection pipes of high-pressure 

 steam-engines, on their discharge, appears to possess the qua- 

 lities of a projectile, notwithstanding its unfavourable form ; 

 and is also carried forward through the air, partly on the 

 rocket principle, by means of the rotary action by which the 

 circular axis of the ring is involved ; the line of progress in 

 this case being in the direction which is perpendicular to the 



