SAFETY LAMP. 281 



A. Because it is generated in 

 meadows and marshes from putrefying 

 vegetable substances. (See ignis fatuus, 

 p. 285). 



Q. What gas is evolved by the WICK of a 

 burning CANDLE ? 



A. Carburetted hydrogen gas: that 

 is, the carbon and hydrogen of the tallow 

 combine into a gas from the heat of the 

 flame ; and this gas is carburetted 

 hydrogen, or inflammable air. 



Q. Why do COAL-MINES so frequently 

 EXPLODE ? 



A. Because the carburetted hydrogen 

 gas (which is generated in these mines 

 by the coals) explodes, when a light is 

 incautiously introduced. 



Q. How can miners SEE in the coal-pits, if 

 they may NEVER introduce a LIGHT ? 



A. Sir Humphrey Davy invented a 

 lantern for the use of miners, called " the 

 Safety Lamp," which may be used 

 without danger. 



Q. Who was SIR HUMPHREY DAVY ? 



A. A very clever chemist, born in 

 Cornwall. (17781829). 



sa 3 



