134 HEATING. 



Much of the apparent complexity which exists on this head 

 arises from the disproportion between the relative volumes, or 

 folk, of the constituent atoms of the several gases, as compared 

 with their respective weights. 



For instance, an atom of hydrogen (meaning the smallest 

 ultimate division into which it is supposed to be resolvable) is 

 double the bulk of an atom of carbon vapor ; yet the latter is 

 $ix times the weight of the former. 



Again, an atom of hydrogen is double the bulk of an atom of 

 oxygen ; yet the latter is eight times the weight of the former. 



So of the constituents of atmospheric air, nitrogen and 

 oxygen. An atom of the former is double the bulk of an atom 

 of the latter ; yet, in weight, it is as fourteen to eight. 



A further source of apparent complexity arises from the 

 faculty of condensation, or diminution of bulk, which, in certain 

 cases, attends the union of the gases. For example, one volume 

 of oxygen and two volumes of hydrogen, when united, condense 

 into a volume equal to that of the hydrogen alone, (the weight 

 being, of course, the sum of both ;) that is to say, one cubic 

 foot of oxygen chemically combined with two cubic feet of 

 hydrogen condense into the bulk of two cubic feet : and so on, 

 each union bearing its now ratio of volume and weight. This 

 apparent complexity, however, we shall soon see give way to a 

 systematic consideration of the subject. 



We have stated that there are two descriptions of hydro-carbon 

 gases, in the combustion of which we are concerned ; both being 

 generated in the furnace, and even at the same time, namely, 

 the carburetted and bi-carluretted hydrogen gases. For the 

 sake of simplifying the explanation, I will confine myself to the 

 first, as forming the largest proportion of the gas to be consumed, 

 namely, the carburetted hydrogen, or common coal gas, as I shall 

 call it for the sake of brevity. 



Now as, during combustion, the atoms of this gas become 

 decomposed, and its constituents separated ; and as these will 

 be found to exercise separate influences during the process, it is 

 essential that we examine them as to their respective properties, 

 weights, and volumes. 



On analyzing this mixed gas we find it to consist of two vol- 



