444 MECHANICAL AGENCIES OF 



it issues from a ball of copper, similar phe- 

 nomena occur. The spark also acquires new 

 particles from the metal through which it passes. 

 In all such cases, the colour of the spark de- 

 pends on the nature of the metal thus ignited 

 from which Fusinieri concludes, that electric 

 light is always combined with ponderable matter; 

 and that lightning owes its luminosity and odour 

 to the combustion of such matter. (Giornale del 

 Pavia, 1825.) 



Dr. Priestley relates, that when the steeple of 

 St. Bride's church in London was torn by a flash 

 of lightning, it acted as an elastic fluid ; and that 

 its effects were exactly similar to what would 

 have been produced by gunpowder pent up in 

 the same places and exploded. 



It is also related by Mr. Lyell, on the autho- 

 rity of Dr. Hibbert, that at Funzie, in Fetlar, 

 one of the Shetlands, about the middle of the 

 last century, a rock of mica schist, one hundred 

 and five feet long, ten feet broad, and in some 

 places four feet thick, was torn in an instant, by 

 a flash of lightning, from its bed, and broken 

 into three large, and several smaller fragments. 

 One of these, twenty-six feet long, ten feet 

 broad, and four feet thick, was simply turned 

 over. The second, which was twenty-eight feet 

 long, seventeen broad, and five in thickness, 

 was hurled across a high point, to the distance 

 of fifty yards. Another broken mass, about 



