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facts by him noticed, that this deterioration was not the consequence 

 of the direct conducting power of the mixture of air and aqueous va- 

 pour, within which the apparatus was situated, but of the adjacent 

 solid surfaces thereby moistened, Dr. Hare determined to ascertain 

 by experiment, whether the view taken by Dr. Mitchell was correct, 

 being the more encouraged to expect an affirmative issue, from the co- 

 pious evolution of electricity which had been recently ascertained to 

 take place during the condensation of high steam. 



Dr. Hare proceeded to describe his experiment. A cup of hot wa- 

 ter, to supply vapour, was placed within a large bell glass, having an 

 open neck of above three inches in diameter; so that the centre of the 

 neck might be immediately under the positive conductor of a large 

 electrical machine. A knob, communicating with the negative con- 

 ductor, was supported in the centre of the bell glass. Next a red-hot 

 rod of iron, terminating in a knob, was suspended by a wire from the 

 positive conductor, so as to descend, concentrically, through the neck, 

 until within striking distance of the knob above mentioned. 



It will be perceived that, in consequence of the high temperature of 

 the rod, and the heat radiating from it to the neck of the bell glass, 

 no moisture could condense upon either, so as to impair the power of 

 the former to give sparks, or of the latter to act as a non-conductor. 



The apparatus being thus prepared, and the machine in operation, 

 sparks were found to pass through the foggy air occupying the cavity 

 of the bell glass, as if no moisture had been present. 



Dr. Hare conceived that the fact that the aqueous vapour does not 

 impair the insulating power of air, must justify some important me- 

 teorological inferences. It was well known that pith balls and other 

 light bodies separate when under the effect of electrical excitement, 

 and it had been justly assumed that the circumambient air must be 

 similarly affected. Thus, when, by its condensation, aqueous vapour 

 evolves electricity, as it does not destroy the insulating power of the 

 air, the aerial particles must be surcharged with that fluid. But, since 

 charging with electricity must cause, in those particles, a disposition to 

 remove from each other to a greater distance, the air must occupy a 

 greater bulk, in proportion as it is more highly charged : in other 

 words, it must be rarefied, and rendered specifically lighter. Hence 

 it will rise to a greater elevation than its temperature, unassisted by 

 electrical reaction, would enable it to reach. It follows that a sudden 

 discharge of electricity, such as is productive of lightning, by causing 

 a sudden augmentation of gravity, may induce a descent of the mass 

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