THE EFFECTS OF LIGHTNING. 



67 



of gunpowder which has been fired. In this case the wire was probably burned. 

 Another wire, in the same tower, of the thickness of a goosequill, transmitted 

 the lightning without being fused. 



When Captain Cook was anchored in the roadstead of Batavia, his ship was 

 struck by lightning, which produced a shock like that of an earthquake. An 

 iron wire, a quarter of an inch in diameter, extending from the mast-top to the 

 water, appeared for a moment to be on fire. No damage was sustained. 



On the 18th of June, 1782, lightning struck the house of Mr. Parker, at 

 Stoke-Newington, near London, and having passed down one of the pipes, pro- 

 vided to conduct the fluvial waters from the roof, from that it passed into a bed- 

 chamber, where it followed the course of a wire which connected a cord at the 

 bedside with a night-bolt at the door, by which a person could bolt or unbolt 

 the door without leaving the bed. Such a bolt passes through two rings at- 

 tached to the doorframe, which, in this case, served as a gauge for the length 

 of the connecting wire. After the lightning had passed along it, the wire w r as 

 found so much shortened that the bolt could not be let fall. 



Wire extended between two fixed points is often broken by lightning, which 

 may be explained by the contraction just mentioned, and the fixed points not 

 allowing the wire to yield. 



IV. OF VITRIFICATIONS AND FULGURITES. 



As evidence of the heights at which the presence of lightning has been man 

 ifested, the vitrifications observed in certain places have been already mention' 

 ed. Saussure, in 1787, observed these effects on the Dome de Goute, one of 

 the summits of Mont-Blanc. Ramond observed them on several summits of the 

 Pyrenees, especially the Pic du Midi and Mont-Perdu, and on the rock Sana 

 doire, in the Puy-de-D6me. Humboldt and Bonpland found similar appearan- 

 ces on the rock El Frayle, at the top of Teluca, one of the Cordilleras, near 

 the city of Mexico. 



These several observers merely saw the vitrifications ; they inferred their 

 cause by the form of reasoning called, in logic, a disjunctive syllogism ; that is, 

 by severally rejecting every other possible cause, they concluded that lightning 

 must have been the true one. That a question so important may not rest solely 

 on such negative proof, M. Arago has collected the following facts in support 

 of it :— 



On the 3d of July, 1725, at Mixbury, in Northamptonshire, lightning struck 

 on an open field, and killed a shepherd and five sheep. Close to the body of 

 the man were found two holes, five inches in diameter and forty inches deep. 

 Near the bottom of one of them ^as found a very hard stone, measuring ten 

 inches long, six inches broad, and four inches thick, with its surface vitrified. 



In the year 1750 lightning struck the tower of Asinelli, at Bologna, and did 

 some injury to it. Beccaria, who examined it, found the bricks at the place 

 where the lightning struck vitrified. 



On the 3d of September, 1789, lightning struck an oak in the park of Lord 

 Aylesford, and killed a man who sought shelter under it. This person carried 

 a walking-stick, which apparently conducted the lightning to the ground, for at 

 its point was found a hole five inches in depth and two inches and a half in di- 

 ameter ; and below this, to a depth of twelve inches, were found marks of vit- 

 rification. 



The fact last mentioned leads to the consideration of fulminary tubes, ox ful- 

 gurites, of which it may almost be regarded as an example. 



The tubes were first discovered in 1711, by Heman, a shepherd, at Massel, 

 in Silesia. Specimens of them were sent to the mineralogical museum at 



