Whirlwinds excited by Fires. S7 



horizontal direction. But the spire of a cohimnar vortex, exhibits 

 a penetrating and ascending power which far exceeds, both in its 

 intensity and the extent of its action, any other ascending move- 

 ment that we witness in the atmosphere. This effect appears to 

 be owing to the spiral motion of the column, which presses on- 

 ward in the direction of its axis, until it reaches a limit of eleva- 

 tion which is yet unknown. Even the 7^ing vortex, which is some- 

 times seen to form at the muzzles of cannon or the ejection pipes 

 of high pressure steam engines, on their discharge, appears to pos- 

 sess the qualities of a projectile, notwithstanding its unfavorable 

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

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

 cular axis of the ring is involved ; the line of progress in this case 

 being in the direction which is perpendicular to the plane of the 

 ring.* On the proximate causes and modus operandi of this as- 

 cending action in the columnar vortex, we cannot now dwell. 



5. The analogy of the foregoing cases to those violent columnar 

 whirlwinds which are so often formed over the craters of active 

 volcanoes, and the apparent identity of the causes which produce 

 them,, well deserve our notice. We may hence comprehend the 

 manner in which volcanic ashes, having no projectile qualities, 

 are carried to a vast height in the atmosphere, and become wafted 

 to a great distance by the different currents of the atmosphere 

 into which they successively subside. The loud roaring noise 

 and thundering detonations, which usually attend these volcanic 

 exhibitions, are also illustrated to some small extent, by the cases 

 before us. 



6. It appears that these cases were attended by electric explo- 

 sions or detonations, and that, apparently, there was only wanting 

 the contact of more extensive masses of the higher and lower at- 

 mosphere, and the presence of a larger body of aqueous condensa- 

 tion, as in the case of the so called thunder cloud which so common- 

 ly attends the naturally formed vortex, in order to have produced 

 the phenomena of genuine thunder and lightning, on a most mag- 



* The vortex here described is also produced in a beautiful manner, by the burn- 

 ing of bubbles of pbosphuretted hydrogen gas, as they escape from water. In this 

 case the peculiar movements of the ring vortex, as well as the sustaining and ex- 

 panding power which appears to Ijelong to aerial vortices, may be advantageously 

 observed. 



Vol. XXXVI, No. 1 .— Jan.-April, 1839. 8 



