190 WRITINGS OF JOSEPH HENRY. [1840 



The results obtained by the philosophers, 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 vaporization of the water were shown to be the source 

 of the electricity, Prof. Henry thought the phenomena might 

 be readily explained by the beautiful theory of Becquerel, in 

 regard to the production of the great intensity of the electri- 

 city in the thunder cloud. According to this theory, each 

 particle of the vapor 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 vapor in a cloud affords a con- 

 tinuous conductor, and consequently the electricity of all 

 the particles of the interior, according to the well known 

 principles of distribution, rushes to the surface of the cloud, 

 and hence the great intensity of the lightning. Agreeably 

 with 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 electricit}'- of the vapor. 



Prof. Henry further stated, in relation to 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 steamboat 

 on the Ohio, which afforded amusement to all the passen- 

 gers, 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 inclined to believe that electricity may also 



