METEOROLOGICAL CORRESPONDENCE. 409 



case, a negro man standing imder a tree during a thunder-storm was struck with 

 lightning and instantly killed ; bat the surprising part of the occurrence was the 

 fact that his woolly hair was afterwards found, adhering to the branches of the 

 tree, several yards above his head. 



There are also apparently well-authenticated cases in which an image of a 

 body standing before a plastered wall has been transferred to the latter bj a 

 discharge of lightning passing from the one to the other. 



These phenomena, though very surprising, are not inconsistent with well-es- 

 tablished principles of electrical action. It has been fully shown by logical de- 

 duction from theoretical principles, and also abundantly proved by experiment, 

 that the atoms of matter which exist along the path of an electi'ical discharge 

 violently repel each other at the moment of the transit, the greatest intensity of 

 the force being in the direction of the axis of the discharge. The eifect may 

 be illustrated by sending a discharge from an electrical battery through a nar- 

 row slip of tinfoil cut into parts, by passing the blade of a knife across it at in- 

 tervals. The ends of each will be turned back on themselves, indicating thai they 

 have been subjected to a violent repulsive energy. It would appear that at the 

 moment of an electrical discharge through a conductor, each atom becomes for 

 an instant highly charged, and thus exhibits a repulsive force sufficient in some 

 cases to separate the matter into its component parts. If a powerful charge be 

 sent through a brass wire, the compound metal will be dissipated into powder of 

 zinc and copper. But the transfer of matter in the line of the axis of the dis- 

 charge is best shown by placing perpendicularly a plate of polished copper 

 midway between two conductors, at about an inch and a half apart, the ends of 

 the two which are turned towards the plate being covered, one with gold and 

 the other with silver foil ; after a powerful discharge from an electrical battery 

 has been sent throngh the two conductors and the interveuing plate, the gold 

 foil on the one side will be found deposited on the plate, and the silver on the 

 other. Ill this experiment the two metals at the same moment are carried in 

 opposite directions, and, what is still more remarkable, upon minute inspection 

 it will be found that particles of the copper plate have also been sent in 02)posite 

 directions, and deposited on the opposite end of each conductor. The explana- 

 tion may be rendered plain by a reference to the annexed diagram, in which 



+ 



c+ - 



a and b represent the two conductors, and c the intervening cop|:)er plate, while 

 the electrical condition of the several points of the system, at the instant the 

 discharge is about to take place, is indicated by the signs -f- and — . From this 

 diagram it will be evident that if the gold leaf be placed on the end of the con-, 

 ductor a, it will be repelled by this conductor, because both are -f- electrified, 

 and will be attracted to the nearside of the plate, this being — electrified, while a 

 similar efi"ect will be produced on the opposite side of the plate. 



Although the repulsive and attractive action is the most intense in the line of 

 the direction of the axis of the discharge, it takes place also in every direction. 

 This is especially the case when a discharge is passed through air, and to this 

 must be referred the surprising mechanical efiects exhibited when a powerful 

 discharge of lightning traverses a confined portion of air. In one instance, 

 which came under my own observation, a stroke of lightning fell upon the 

 chimney on the west end of a house ; broke through the flue into the cock-loft 

 or space immediately under the roof, and, passing through this a distance of 

 aOout twenty feet, entered the flue of another chimney on the east end, in which 

 was a stove-pipe, and descended to the earth. In its passage through the 

 cock-loft, the particles of air near or in its path were rendered in an instant 

 so mutually repulsive that they separated with such explosive energy as to lift 

 up bodily the whole roof. 



