PHOSPHURETTED HYDROGEN. 283 



ignites and burns inside the lamp: as 

 soon, however, as this is the case, the 

 miner is in danger, and should withdraw. 



Q. Why is the miner in DANGER, if the gas 

 ignites and burns in the INSIDE of the safety-lamp ? 



A. Because the heat of the burning 

 gas will soon destroy the wire gauze, and 

 then the flame (being free) will set fire 

 to the mine. 



CHAPTER XXI. 



PHOSPHURETTED HYDRO- 

 GEN GAS. 



Q. From what does the very OFFENSIVE 



EFFLUVIA Of CHURCH- YARDS arise ? 



A. From a gas called PHOSPHURET- 

 TED HYDROGEN; which is phosphorus 

 combined with hydrogen gas. 



Q. What is PHOSPHORUS ? 



A. A pale amber-coloured substance, 



