1850] 



WRITINGS OP JOSEPH HENRY. 293 



come highly negative, while the other end of the same con- 

 ductor must be highly positive ; also, the first end of the 

 second conductor will be negative, and the other end posi- 

 tive, and so on. The lightning therefore will enter the 

 metal with much greater intensity than that with which it 

 will pass along the conductor ; and hence a hole may be 

 melted at the point of entrance ; for the same reason another 

 hole might be expected at the point of exit, and in this way 

 the perforations of the pans might be explained. The elec- 

 tricity did not pass through the space from side to side of 

 the pan, as a bullet would have done, but took the circuit 

 around the inverted bottom of the vessel. 



He stated that in all cases when an electrical discharge 

 passes through a conductor, the point at which the fluid en- 

 ters, and that at which it passes out, are both marked with 

 evidence of more intense action. 



When a disruptive discharge takes place through the air 

 between two conductors, in many cases a part of the matter of 

 each conductor is transferred to the other. Professor Henry 

 said that he had received accounts from different sources of a 

 remarkable phenomenon connected with this action. In the 

 case of a person killed many years ago by lightning, while 

 standing near to the whitewashed wall of a room, the dis- 

 charge took place between his body and the wall, and on 

 the latter was depicted, in dark color, an image of his per- 

 son. Other cases of the same kind had been observed. 



ON THE PHENOMENA OF THE LEYDEN JAR. 

 (Proceedings American Association, Adv. of Science, vol. iv, pp. 377, 378.) 



August 24, 1850. 



Professor Henry gave an account of his investigation of 

 the discharge of a Leyden jar. This was a part of a series 

 of experiments he had made a few years ago on the general 

 subject of the dynamic phenomena of ordinary or frictional 

 electricity. On this subject he had made several thousand 

 experiments. He had never published these in full, but had 

 given brief notices of some of them in the Proceedings of 



