376 Scientific Intelligence — Meteorology. 



to conduct silently the most violent dischai-ge which may fall from 

 the clouds. 



Professor Henry also stated, that he had lately examined a house 

 struck by lightning, which exhibited some effects of an interesting kind. 

 The lightning struck the top of the chimney, passed down the interior 

 of the flue to a point opposite a mass of iron placed on the floor of the 

 garret, where it pierced the chimney ; thence it passed explosively, 

 breaking the plaster, into a bedroom below, where it came in contact 

 with a copper bell-wire, and passed along this horizontally and quietly 

 for about six feet; thence it leaped explosively through the air a distance 

 about ten feet, through a dormer window, breaking the sash, and 

 scattering the fragments across the street. It was evidently attracted 

 to this point by the upper end of a perpendicular gutter, which was 

 near the window. It passed silently down the gutter, exhibiting 

 scarcely any mark of its passage until it arrived at the termination, 

 about a foot from the ground. Here, again, an explosion appears to 

 have taken place, since the windows of the cellar were broken. A 

 bed, in which a man was sleeping at the time, was situated against 

 the wall, immediately under the bell-wire ; and although his body 

 was parallel to the wire, and not distant from it more than four feet, 

 he was not only uninjured, but not sensibly afiected. The size of the 

 hole in the chimney, and the fact that the lightning passed along the 

 upper wire without melting it, shew that the discharge was a small 

 one, and yet the mechanical effects in breaking the plaster, and pro- 

 jecting the window frame across the street, were astonishingly great. 



These effects the Professor attributes to a sudden repulsive energy, 

 or expansive force developed in the air along the path of the dis- 

 charge. Indeed, he conceives that most of the mechanical effects 

 which are often witnessed in cases of buildings struck by lightning, 

 may be referred to the same cause. In the case of a house struck 

 within a few miles of Princeton, the discharge entered the chimney, 

 burst open the flue, and passed along the cockloft to the other end of 

 the house ; and such was the explosive force in this confined space, 

 that nearly the whole roof was blown off. This effect was, in all 

 probability, due to the same cause which suddenly expands the air in 

 the experiment with Kinnersly's electrical air-thermometer. 



Dr Patterson stated, that Mr Jefferson was of the opinion that 

 metal roofs protected buildings, not from being struck, but from the 

 danger of the stroke. The contrary opinion is generally held ; but 

 Professor Henry's experiments shew that Mr Jefferson was correct. 

 Dr P. saw the lightning strike a row of dormitories with metal roofs, 

 at the University of Virginia. The flash was very severe, but pro- 

 duced no evil effect ; the lightning had spread itself over the surface, 

 and left its mark at each interruption of the conductor, but did no 

 damage. It was said at the University that the Rotunda had been 

 frequently struck without injury. — (Proceedings of the American Phi- 

 losophical Society, vol. iv., No. 33, p. 179-) 



