On the Causes of the Tornado, or Water Spout. 161 



discussion sur ce point nous serablerait prematuree ; il faut multiplier 

 les observations, et constater avec plus de precision toutes les circon- 

 stances de ces phenoraenes."* 



All the information respecting tornadoes afforded by Despretz is 

 comprised in the following paragraphs, which I quote in his own words. 



" Trombe. La trombe se montre en mer et sur la terre; tantot 

 elle semble sortir du sein de la mer, et s'eleve jusqu'aux nuages; tan- 

 tot elle descend des nuages jusqu'a terre. 



"C'est une colonne d'eau conique qui tourne sur elle-meme avec 

 une grande vitesse; elle a quelquefois jusqu'a plus de deux cents 

 metres de base. Elle est tres-commune entre les tropiques : les nav- 

 igateurs passent rarement pres des cotes de Guinee sans en aperce- 

 voir plusieurs. 



" Les trombes produisent des efFets terribles ; elles deracinent les 

 arbres, renversent les faibles habitations, soulevent les voitures, etc. 



" On pent se faire une idee des trombes par les tourbillons de pou- 

 issiere qui se forraent tout a-coup, en eie, sur les routes, et qui tour- 

 nent sur eux-memes avec une grande rapidite."-{- 



In Nicholson's Journal, quarto series, London, 1797, vol. 1, page 

 583, there is an interesting account of some tornadoes seen from 

 Nice, illustrated by engravings, by M. Michaud, who appears to con- 

 sider them as the effect of electricity, and infers that he could produce 

 the phenomenon in miniature by the aid of a machine, as thunder 

 and lightning are by the same means illustrated. This I have found 

 to be erroneous, as far as my experience goes, and from a cause 

 which is, agreeably to my hypothesis, quite evident. I mean the 

 absence of the co-operating influence of the air when emancipated by 

 electric attraction from the confinement arising from its own weight. 



The theoretic remarks of Michaud are very brief, and, to me, 

 scarcely intelligible, as he does not inform us in what way he suppo- 

 ses the electric fluid to operate. 



I have understood, since I conceived my hypothesis, that Beccaria 

 ascribed water spouts to electricity, but I have not had the advantage 

 of learning by what reasoning he justified his inferences. However, 

 should it appear that I have made, through the want of information, 

 any undue claim to priority, I shall cheerfully do justice to any phi- 

 losopher whose speculations I may have overlooked. 



* Elemens de Physique Experimentale et de Meteorologie, vol. 2, p. 727. 

 + Traite Elementaire de Physique, paragraph 656, p. 828, par C. Despretz. 



Vol. XXXIL— No. 1. 21 



