136 Additional Objections to Medfield^s TJceory of Storms. 



per hour. There appears to have been within the sphere of its 

 violence an area, throughout which the barometric cokimn stood 

 at a minimum, and towards which the wind blew violently on 

 the one side only from between east and south, and on the other 

 only between north and west. This area extended from south- 

 west to northeast more than two thousand miles. Its great length 

 in proportion to its breadth seems irreconcilable with its having 

 formed the axis of a whirlwind. The course of this storm, as 

 above stated, was at right angles to that attributed by Redfield to 

 storms of this kind. (Trans, of the American Philos. Society, 

 Yol. 7.) 



79. Having said so much against the whirlwind theory of 

 storms, it may be expected that I should, on this occasion, say 

 something respecting the opinions which I entertain of their ori- 

 gin. To a certain extent this will be found in my communica- 

 tions published in this Journal, Vol. xxxii, p. 153, Vol. xl, p. 137, 

 also in my essay on the gales of the United States. I still be- 

 lieve our northeastern gales were correctly represented in the last 

 mentioned essay as arising from an exchange of position made 

 between the air of the Gulf of Mexico and that of the territory 

 of the United States which lies to the northeast of that great 

 estuary; and that the heat given out during the conversion of 

 aqueous vapor into rain, by imparting to the atmosphere as 

 much caloric as could be yielded by twice its weight of red 

 hot sand, is a great instrument in the production of the phenom- 

 ena; also, that the cold resulting from rarefaction is a cause of 

 the condensation of that vapor, and of course of clouds. On this 

 last idea, derived from Dalton, Mr. Espy has founded his ingen- 

 ious theory of storms ; alleging, erroneously, as I think, the buoy- 

 ancy, resulting from the heat thus evolved, to be the grand cause 

 of rain, also of tornadoes, hurricanes, and other electrical storms. 

 In the essay above mentioned, I erred in ascribing too much 

 to variations of density arising from changes of elevation, and 

 twenty years' additional experience as an experimenter in electri- 

 city, has taught me to ascribe vastly more to this agent than I 

 did formerly. To pursue this subject fully, would give this pa- 

 per an undue length ; yet I will subjoin a series of suggestions 

 which in September last were submitted to the Royal Academy 

 of Sciences at Paris. These will serve to give a general idea of 

 the views which I entertain of the electrical causes of storms. 



