PRINCIPLES OF COMBUSTION. 145 



volume of gas, and why neither more nor less will satisfy the 

 conditions of its combustion. For, if more, the excess, inde- 

 pendently of the mischievous chemical unions that might enter 

 into it in the furnace, would be the means of carrying away as 

 much heat as it would take up by its expanding faculty. And 

 if less, a corresponding quantity of either hydrogen or carbon 

 would be deficient of its supporter, and necessarily pass off 

 uncombined and unconsumed. 



The only observation here necessary to make on the difference 

 between these two gases is, that as this latter gas contains two 

 atoms of carbon instead of one, it follows that a proportionate 

 additional quantity of oxygen will be required for this additional 

 atom of carbon. Hence, if carburetted hydrogen requires two 

 volumes of oxygen for combustion, the bi-carburetted hydrogen 

 will require three volumes. And so of air : if ten volumes of 

 air are required for the one gas, fifteen volumes are consequently 

 required for the other gas. 



4. We have seen that, in the formation of the carburetted 

 hydrogen, a considerable portion of the carbonaceous constituent 

 of fuel is separated, and carried away by the hydrogen in the 

 gaseous form, forming the carburetted hydrogen ; the remainder 

 of such carbonaceous matter is what we have now to deal with ; 

 the difference as regards combustion between these two portions 

 of carbon being so important as to demand especial notice. 



In observing this curious arrangement by which the saturation 

 of the combustible atoms is effected, we perceive that three atoms 

 of the combustible are apportioned to four of the supporter. 

 This, we see, is the result of one atom of carbon requiring two 

 of the supporters, while the two of hydrogen are satisfied with 

 one each. 



Now, in this arrangement no excess or deficiency appears 

 among the heat-producing ingredients. Could we have dis- 

 pensed with or avoided the presence of such an excess of nitro- 

 gen, (which is neither a combustible nor supporter of combus- 

 tion,) the several unions would have been less embarrassed, 

 their combustion more rapid and complete, and the intensity 

 of their action much increased. That, however, was impossible. 



