448 ELECTRIC LIGHT. 



Prussia and Silesia, large glass tubes are fre- 

 quently found in banks of sand, from twenty to 

 forty feet in length, formed by the sudden fusion 

 of silicious matter by flashes of lightning; and, 

 as might naturally be supposed, that the inner 

 surface of these fulminary tubes is smooth, while 

 the outside is rough. In regard to the mechan- 

 ical effects of lightning in rending trees, displac- 

 ing large rocks, and perforating the walls of 

 buildings, the community is generally more or 

 less informed. 



Again ; like caloric, electricity expands all bodies 

 into flame or light. But Sir I. Newton, and after 

 him Sir H. Davy, defined flame as gaseous 

 matter raised to a red or white heat : from which 

 it would seem that they both regarded flame as a 

 modification of ponderable matter. And I have 

 already shewn that all bodies may be converted 

 into light, whether by heat or electricity ; and 

 that its colour varies according to the nature of 

 the ponderable matter employed;* that potas- 

 sium, strontium, lithium, boron, and some other 

 bodies, burn with a red light ; hydrochlorate of 

 calcined soda, with an orange light ; oil, tallow, 

 and resins, with a yellow light ; hydrogen 



* Much additional information might be obtained on this im- 

 portant subject, by submitting all the elements of ponderable 

 matter to the agency of voltaic electricity, separately in succes- 

 sion ; and by analyzing their light with a prism, or by causing it 

 to pass through differently coloured transparent media. 



