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LXVIII. On the Theory of Cyclones, Waterspouts, fyc. By 

 Thomas Dobson, B.A., Head Master of the High School of 

 Hobart Town, Van Diemen's Land. 



OUR knowledge of cyclones is limited to that mature condition 

 of the phenomenon in which it has become a hurricane : 

 nothing is known of their origin, and very little of their gradual 

 development. It might be anticipated that some light would be 

 thrown on these important points by investigating and comparing 

 the corresponding phases of the apparently analogous pheno- 

 mena of waterspouts, tornados, &c. This comparison seems to 

 have been somewhat too hastily abandoned by cyclonologists on 

 meeting with some cases in which the law of rotation appeared 

 to be violated. If this discrepancy had been well established, it 

 might be thought fatal to the hypothesis of the homogeneity of 

 the two meteors ; but the observations of the direction of rotation 

 of waterspouts are both too few- and too uncertain to outweigh 

 the numerous remarkable coincidences which tend to show that 

 cyclones and waterspouts differ only in degree ; a waterspout being 

 either a cyclone in miniature, or an embryo cyclone. In several 

 instances two or three waterspouts have been seen within the 

 area of one cyclone, which confirms the supposition that both 

 meteors are produced by the same physical agent. Each has a 

 motion of rotation about a vertical axis, and another of transla- 

 tion along the surface of the earth. Both arise after extreme 

 heat, and travel towards a colder region. The central portions 

 of both are characterized by an excessively low temperature and 

 extreme rarefaction ; by copious falls of rain, snow and hail ; by 

 peculiar noises; by lightning, and other manifestations of the 

 presence of electricity. Further research will disclose more 

 points of close resemblance. An inquiry into the origin and 

 nature of waterspouts, tornados, and other apparently cognate 

 phenomena, may therefore lead to valuable suggestions respect- 

 ing the more important but less known phenomenon called a 

 cyclone. 



The following appear to be the main facts which are available 

 as a basis for a theory which shall comprehend all the meteors 

 in question. 



1. The eruption of a submarine volcano has produced waterspouts. 



" During these bursts the most vivid flashes of lightning con- 

 tinually issued from the densest part of the volcano, and the 

 columns of smoke rolled off in large masses of fleecy clouds, 

 gradually expanding themselves before the wind in a direction 



