XXXVhl INTRODUCTION. 



Here we should compare the theory of Mr. Espy with other 

 theories, anterior or contemporaneous. The labors of Franklin, 

 and of Messrs. Redfield, Reid, and Peltier would furnish as many 

 excellent observations and parts, or the whole of the phenomena, 

 very well studied. But the extensive discussion which we should 

 have to establish before deciding in favor of Mr. Espy, would lead 

 us too far. Mr. Espy himself, as to the electrical part of the phe- 

 nomenon, which, however, he regards as only accessory and se- 

 condary, acknowledges that his theory is less advanced and less 

 complete than it is with regard to the phenomena of the motion 

 and precipitation of the water, which are, according to him, the 

 base of the production of the meteor. 



Finally, it is proved by the investigations of Mr. Espy, that it 

 will be impossible hereafter to adduce in the mean [normale] 

 state of the atmosphere, a descending current of air as a cause of 

 cold, or an ascending current of dry air, a cause of heat. The 

 applications of this theory present themselves in " climatology," 

 but this principle especially discards the idea of explanation of the 

 tornado by the centrifugal force, which would then cause the up- 

 per air to descend in the centre of the tornado, which air becom- 

 ing heated by the augmented pressure, could not allow its own 

 vapor to be precipitated nor precipitate that of the air with which 

 H came in contact. 



CONCLUSION. 



In conclusion, Mr. Espy's communication contains a great num- 

 ber of well-observed and well-described facts. His theory, in the 

 present state of science, alone accounts for the phenomena, and, 

 when completed, as Mr. Espy intends, by the study of the action 

 of electricity when it intervenes, will leave nothing to be desired. 

 In a word, for physical geography, agriculture, navigation, and 

 meteorology, it gives us new explanations, indications useful for 

 ulterior researches, and redresses many accredited errors. 



The committee expresses then, the wish "that Mr. Espy should 

 be placed by the government of the United States in a position to 

 continue his important investigations, and to complete his theory, 

 already so remarkable, by means of all the observations and all 

 experiments which the deductions even of his theory may suggest 

 to him, in a vast country, where enlightened men are not wanting 

 to science, and which is besides, as it were, the home of these 

 fearful meteors. 



The work of Mr. Espy causes us to feel the necessity of under- 

 taking a retrospective examination of the numerous documents 

 already collected in Europe, to arrange them and draw from them 

 deductions which they can furnish, and more especially at the 

 present period, when the diluvial rains, which have ravaged the 

 south east of France, have directed attention to all the possible 



