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that he had obtained feeble electricity from a small ball, partly filled with 

 water, and heated by a lamp. He agreed with Dr. Patterson in the opi- 

 nion, that the source of the electricity was the change of state, but from 

 water to vapour. There was, however, some doubt on the subject; 

 Pouillet had denied the evolution of electricity from the evaporation of 

 pure water. The facts were interesting, particularly on account of the 

 great intensity of the electricity. The results, obtained by the phi- 

 losophers, which had been mentioned, indicated electricity of very 

 feeble tension, which could only be observed by the most delicate 

 instruments, but here the sparks were an inch in length. If the va- 

 porization of the water were shown to be the source of the electricity, 

 Prof. Henry thought that the phenomena might be readily explained 

 by the beautiful theory of Becquerel, in regard to the production of 

 the great intensity of the electricity in the thunder cloud. According 

 to this theory, each particle of the vapour carries up with it into the 

 atmosphere the free electricity, which it receives at the moment of 

 the change of state: this, being diffused through the whole capacity 

 of the air, is of very feeble intensity, although of great quantity ; but 

 the condensation of the vapour into a cloud affords a continuous con- 

 ductor, and consequently the electricity of all the particles of the in- 

 terior, according to the well known principles of distribution, rushes 

 to the surface of the cloud, and hence the great intensity of the light- 

 ning. According to this hypothesis, the insulated conductor, placed 

 in the steam, would act not only as a collector, but also as a con- 

 denser of the free, but feeble, electricity of the vapour. 



Prof. Henry farther stated, in connection with this subject, that he 

 had been informed by several persons, that they had obtained sparks 

 of electricity from, a coal stove during the combustion of anthracite. 

 A case had been stated to him several years ago, which he mentioned 

 to his friend Professor Bache, who informed him that a similar one 

 had fallen under his own notice, in which, however, Prof. Bache had 

 succeeded in tracing the electricity to the silk shirt of the person who 

 drew the spark. Another case had lately been reported to him by 

 an intelligent gentleman, of a stove burning bituminous coal, on board 

 of a steam-boat on the Ohio, which afforded amusement to all the pas- 

 sengers during the voyage, by giving sparks of electricity whenever 

 it was touched. 



In connection with the facts that had been stated of the production 

 of electricity from steam, Prof. Henry observed that he was now in- 

 clined to believe that electricity may also be evolved during the combus- 



E 



