Mr. T. Belt on the Origin of Whirlwinds. 47 



Vanadlnite after galena, form P. Fig. 22. 



Calamine after vanadinite, form a o, 



fig. 4. 

 Hematite after caleite, form m r, fig. 22. 



Argyllshire. On the east shore of Kerrara 

 Sound, in argillaceous schist, — 



Haematite after pyrites, form P. 

 The centres of these pseudomorphs, which 

 occur in large quantity, are sometimes hollow. 

 On the island in Kerrara Sound, and on 

 Kerrara, — 



Limnite after pyrites, forms P, Pe. 

 About three miles north-west of East Tar- 

 bet, — 



Magnetite after pyrites, forms P, Pe. 

 Patches of unaltered pyrites occur dispersed throughout the 

 mass of some of these crystals, which are apparently associated 

 with small quantities of pennite and emerald nickel. 



VI. An Inquiry into the Origin of Whirlwinds. 

 By Thomas Belt, Mount Egerton, Victoria*. 



HAVING during the last four years studied the phsenomena 

 of those small eddies of wind common in many parts of 

 Australia during the summer months, and having deduced prin- 

 ciples which are, I believe, applicable to the solution of all, or 

 nearly all, circular movements of the atmosphere, I am induced 

 to lay the results of my observations before your Society, hoping 

 that they may tend to clear up some of the doubts entertained 

 concerning the origin of circular winds. 



Lying, as Melbourne does, within the limits of one of the 

 great hurricane tracks, the subject is one of great importance ; 

 and even if the opinions I am about to lay before you prove 

 erroneous, still good must ensue from the attention of your 

 Society being directed to the subject. 



The small eddies of air of common occurrence in this colony, 

 are examples of the simplest form of a whirlwind. Taking them, 

 therefore, as a starting-point, I shall propose a theory to account 

 for their violence and circular action, and then seek to apply the 

 same to the elucidation of the grander convulsions of the at- 

 mosphere. 



Much of my reasoning must of necessity be from analogy ; 



* Read before the Philosophical Institute of Victoria, December 185/ ; 

 communicated by the Astronomer Royal. 



