66 



THE EFFECTS OF LIGHTNING. 



by lightning in the neighborhood of Castres. The blade of the sword which 

 he wore was fused upon its surface at several places, while the scabbard con- 

 taining it was not burned. This circumstance is not inconsistent with the 

 known properties of bodies. The part of the blade not fused being a good 

 conductor of heat, abstracted the heat from the fused part before it had time to 

 burn the scabbard. 



The statements of the ancient writers above quoted being taken literally, led 

 Franklin to adopt the hypothesis of cold fusion. To admit the possibility of a 

 wooden scabbard containing the heavy mass of incandescent liquid metal which 

 must have resulted from the fusion of a Roman sword without being burnt, 

 was impossible. He therefore proposed to remove the difficulty by admitting 

 that lightning possesses the property of melting metals without heating them. 

 This affords one of the many instances of the errors which arise from framing 

 hypotheses to explain phenomena, the existence and nature of which are not 

 accurately ascertained. The strict rules of philosophical reasoning required 

 that Franklin should demonstrate as a matter of fact that the metal liquefied by 

 lightning is actually cold while in the state of fusion. 



> That lightning fuses metals by raising their temperature to the point of fu- 



> sion, is proved by the fact that metal fused by lightning falling in liquid drops 

 j on a wooden floor, or on the deck of a vessel, has bmnt holes in the wood. 



The fusion effected by lightning is not confined to that of thin wire or to 

 the slight superficial fusion above mentioned. Considerable masses of metal 

 have been on various occasions melted. When the power has not sufficient 

 energy to produce fusion, the iron is often rendered incandescent and soft, and 

 reduced to the state necessary for welding it. With a still more feeble power, 

 it is only raised to a temperature more or less elevated. The following facts 

 are collected by M. Arago in illustration of these principles : 



On the 20th of April, 1807, at Great Mouton,in Lancashire, a windmill was 

 struck with lightning, which, having passed along a large iron chain, softened 

 the links, so that by their own weight they were welded together, and the 

 chain was converted into a rod of iron. 



In June, 1829, the same occurrence took place in a windmill at Lothill, in 

 Essex. 



On the 5th of April, 1807, at Vezinet, near Paris, lightning struck a key, 

 and softened it so that, by its weight, it was welded to its ring. 



In March, 1772, lightning struck a bar of iron inserted at the most elevated 

 part of the dome of St. Paul's cathedral, which was intended by the architect 

 to be in metallic connexion with the pipe by which the water is conducted 

 from the roof to the ground. This connexion was accidentally interrupted at 

 a certain point, and there it was found that the bar had been rendered red hot. 

 This bar was four inches broad, and half an inch thick. 



In August, 1777, the weathercock of a tower in Cremona was struck by 

 lightning, and the marble stones of the tower broken and scattered. The 

 thunder was the most violent ever heard in that place. The iron rod of the 

 weathercock, which was half an inch in diameter, was broken, but showed no 

 mark of fusion. 



On the 12th of July, 1770, lightning struck the house of Mr. J. Moulde, in 

 Philadelphia, and fused a rod of copper six inches long, but of unascertained 

 diameter. 



In 1754, the steeple at Newbury, in the United States, was struck by 

 lightning, after which it was examined by Franklin, who found that the light- 

 ning had passed along an iron wire twenty feet long, and about the thickness 

 of a knitting-needle, which it reduced to smoke. The course of the wire 

 along the walls and floors was marked by a black line, like that left by a train 



