Whirlwinds excited by Fires. 377 



plane of the ring.* On the proximate causes and modus 

 operandi of this ascending action in the columnar vortex, we 

 cannot now dwell. 



5. The analogy of the foregoing cases to those violent colum- 

 nar 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 com- 

 prehend the manner in which volcanic ashes, having no pro- 

 jectile qualities, are carried to a vast height in the atmosphere, 

 and become wafted to a great distance by the difterent cur- 

 rents 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 ex- 

 plosions or detonations, and that, apparently, there was only 

 wanting the contact of more extensive masses of the higher 

 and lower atmosphere, and the presence of a larger body of 

 aqueous condensation, as in the case of the so-called thunder 

 cloud which so commonly attends the naturally formed vortex, 

 in order to have produced the phenomena of genuine thunder 

 and lightning, on a most magnificent scale. This effect, it 

 appears, is most fully produced in the volcanic exhibitions 

 above mentioned. 



7. These cases may serve to illustrate, in some degree, the 

 favouring influences which are presented in the calm latitudes, 

 near the equator, and on the exterior limits of the trade winds 

 in mid-ocean, for the production of vorticular action, either in 

 the form of squalls, thunder-gusts, or water-spouts. The 

 main horizontal movements of circulation which are common 

 to our atmosphere, being here comparatively sluggish or inert, 

 opportunity is thus afforded for the minor influences of rarefi- 

 cation to come into play ; by which means, frequent squalls, 

 water-spouts, and other local movements in the lower atmo- 

 sphere, are excited in these regions. 



* The vortex here described it also produced in a beautiful manner, by 

 the burning of bubbles of phosphurcted hydrogen gas, as they escape from 

 ■water. In this ca«e the peculiar movements of the ring vortex, as well as 

 the sustaining and expanding power which appears to belong to aerial vorti- 

 ces, may be advantageouely observed. 



