1852.] Notes on Bust Whirlwinds and Cyclones. 333 



Notes on Bust Whirlwinds and Cyclones. By P. F. H. Badde- 

 ley, Esq., M. B., Bengal Artillery, Lahore. 



(As an Appendix to his last paper, — ante p. 264.) 



1. — My experience of the smaller dust whirlwinds leads me to 

 believe, that they travel uninfluenced by the direction of the prevail- 

 ing surface wind which may have been blowing prior to their appear- 

 ance, and indeed, they often come up from an opposite point of the 

 compass. 



If they are, as I am certain is the case, themselves the exciting 

 cause of wind, the reason of this is obvious. 



2. — They rarely deviate materially from their original course, 

 though they commonly progress, more or less, in a wavy line ; — now 

 on one side of the path, and now on the other. 



3. — They turn indifferently from left to right, or from right to left, 

 and their rotatory motion sometimes seems suddenly reversed — though 

 this may be only an optical illusion. 



4. — During strong winds, and in stormy weather, the spiral columns, 

 though in full force, are not easily recognisable, even when passing 

 over a light, dry soil ; and would be entirely unnoticed by most per- 

 sons. 



5. — When numerous, they are frequently observed advancing in a 

 line ; and after passing the observer, an interval of some minutes may 

 elapse before another set is seen in the distance — and so they con- 

 tinue — one set succeeding another, giving rise to squalls and lulls, 

 or rising and falling of the wind, 



6. — Their rate of progression is liable to great variety — being some- 

 times retarded and then again accelerated, without apparent cause : 

 but in a brisk wind their progress is more uniform. 



7. — They appear with great regularity between, though sometimes 

 a little before and after, the hours of 10 a. m. and 4 p. m., increas- 

 ing in frequency with the heat of the day, and declining as the sun 

 approaches the western horizon : — ceasing altogether before sun-set, 

 when the wind drops. 



From the fact of their appearing in greatest numbers during the 



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