CHEMICAL HISTORY OF A CANDLE 145 



Thus far we have tested this power of oxygen, and the 

 high combustion it produces by means of other substances. 

 We must now, for a little while longer, look at it as respects 

 the hydrogen. You know, when we allowed the oxygen 

 and the hydrogen derived from the water to mix and burn 

 together, we had a little explosion. You remember also that 

 when I burnt the oxygen and the hydrogen in a jet together, 

 we got very little light, but great heat; I am now about to 

 set fire to oxygen and hydrogen mixed in the proportion in 

 which they occur in water. Here is a vessel containing one 

 volume of oxygen and two volumes of hydrogen. This 

 mixture is exactly of the same nature as the gas we just 

 now obtained from the voltaic battery; it would be far too 

 much to burn at once; I have therefore arranged to blow 

 soap-bubbles with it and burn those bubbles, that we may 

 see by a general experiment or two how this oxygen sup- 

 ports the combustion of the hydrogen. First of all we will 

 see whether we can blow a bubble. Well, there goes the 

 gas [causing it to issue through a tobacco-pipe into some 

 soap-suds]. Here I have a bubble. I am receiving them 

 on my hand, and you will perhaps think I am acting oddly 

 in this experiment, but it is to show you that we must not 

 always trust to noise and sounds, but rather to real facts. 

 [Exploding a bubble on the palm of his hand.] I am afraid 

 to fire a bubble from the end of the pipe, because the explo- 

 sion would pass up into the jar and blow it to pieces. This 

 oxygen, then, will unite with the hydrogen, as you see by 

 the phenomena, and hear by the sound, with the utmost 

 readiness of action, and all its powers are then taken up in 

 its neutralization of the qualities of the hydrogen. 



So now I think you will perceive the whole history of 

 water with reference to oxygen and the air from what we 

 have before said. Why does a piece of potassium decom- 

 pose water? Because it finds oxygen in the water. What 

 is set free when I put it in the water, as I am about to do 

 again? It sets free hydrogen, and the hydrogen burns; but 

 the potassium itself combines with oxygen ; and this piece of 

 potassium, in taking the water apart the water, you may 

 say, derived from the combustion of the candle takes 

 away the oxygen which the candle took from the air, 



