CHEMICAL HISTORY OF A CANDLE 149 



may go on in this way, putting in more and more of the 

 test-gas, until I come to something left behind which will 

 not redden any longer by the use of that particular body that 

 rendered the air and the oxygen red. Why is that? You 

 see in a moment it is because there is, besides oxygen, 

 something else present which is left behind. I will let a 

 little more air into the jar, and if it turns red you will 

 know that some of that reddening gas is still present, and 

 that, consequently, it was not for the want of this pro- 

 ducing body that that air was left behind. 



Now you will begin to understand what I am about to 

 say. You saw that when I burnt phosphorus in a jar, 

 as the smoke produced by the phosphorus and the oxy- 

 gen of the air condensed, it left a good deal of gas unburnt, 

 just as this red gas left something untouched; there was, 

 in fact, this gas left behind, which the phosphorus can not 

 touch, which the reddening gas can not touch, and this 

 something is not oxygen, and yet is part of the atmosphere. 



So that is one way of opening out air into the two things 

 of which it is composed oxygen, which burns our candles, 

 our phosphorus, or any thing else, and this other substance 

 nitrogen which will not burn them. This other part of 

 the air is by far the larger proportion, and it is a very 

 curious body when we come to examine it; it is remarkably 

 curious, and yet you say, perhaps, that it is very uninterest- 

 ing. It is uninteresting in some respects because of this, 

 that it shows no brilliant effects of combustion. If I test it 

 with a taper as I do oxygen and hydrogen, it does not burn 

 like hydrogen, nor does it make the taper burn like oxygen. 

 Try it in any way I will, it does neither the one thing nor 

 the other; it will not take fire; it will not let the taper 

 burn; it puts out the combustion of every thing. There is 

 nothing that will burn in it in common circumstances. It 

 has no smell; it is not sour; it does not dissolve in water; 

 it is neither an acid nor an alkali; it is as indifferent to all 

 our organs as it is possible for a thing to be. And you 

 might say, "It is nothing; it is not worth chemical atten- 

 tion; what does it do in the air?" Ah! then come our 

 beautiful and fine results shown us by an observant phi- 

 losophy. Suppose, in place of having nitrogen, or nitrogen 



