THE HKASON WHY. 



"Oh that men would praise the I^ord for his goodness, and for his wonderful 

 works to the children of men." PSALM cvn. 



a similar process to that by which charcoal is produced. It forms 

 the residue after hydrogen gas has been made from coals. It consists 

 almost entirely of carbon. 



279. Why do burning coals produce yellow flame ? 

 Because the hydrogen which they contain is combined with some 



proportion of carbon, which imparts a bright yellow colour to tho 

 flames. 



280. Why do some of the flames of a flre appear much 

 whiter than others ? 



Because the quality of coals, and the conditions under which 

 they are burnt, are liable to variation. Some coals yield a heavy 

 hydrogen, called bi-carburetted hydrogen, which burns with a 

 much brighter flame than carburetted hydrogen. 



281. Why does bi-carburetted hydrogen burn with a tvhiter 

 flame than the common coal gas ? 



Because it is combined with a larger proportion of carbon, to 

 which it .owes its increased luminosity. 



282. Why do some of tlie flames of a flre appear blue ? 



Because the hydrogen which is escaping where those flames occur 

 is pure hydrogen, destitute of carbon. 



283. Why does the flre sometimes appear red, and without 

 flame? 



Because the volatile gases have been driven off and consumed, 

 and combustion is continued by the carbon of the coals and the 

 oxygen of the air. 



284. Wkat effect has the burning of afire upon the compo- 

 sition of the air ? 



It is found that in burning lOlb. of coal the oxygen contained ia 

 1,551 cubic feet of air is altogether absorbed. It is therefore neces* 

 sary to keep the atmosphere of a room, in which a coal fire a 

 burning, fresh and pure, to supply 155 cubic feet of fresh air fol 

 every pound of coal that is consumed. 



