164 FARADAY 



careous matter, like shells and corals, and many of the rockt 

 and minerals in the earth. But I have not yet told you fully 

 and clearly the chemical history of this substance, carbonic 

 acid, as we have it from the candle, and I must now resume 

 that subject. We have seen the products, and the nature of 

 them, as they issue from the candle. We have traced the 

 water to its elements, and now we have to see where are the 

 elements of the carbonic acid supplied by the candle: a few 

 experiments will show this. You remember that when a 

 candle burns badly it produces smoke; but if it is burning 

 well, there is no smoke. And you know that the brightness 

 of the candle is due to this smoke, which becomes ignited. 

 Here is an experiment to prove this: so long as the smoke 

 remains in the flame of the candle and becomes ignited, it 

 gives a beautiful light, and never appears to us in the form 

 of black particles. I will light some fuel which is extrava- 

 gant in its burning: this will serve our purpose a little 

 turpentine on a sponge. You see the smoke rising from it, 

 and floating in,.o the air in large quantities; and remember 

 now, the carbonic acid that we have from the candle is from 

 such smoke as that. To make that evident to you, I will 

 introduce this turpentine burning on the sponge into a flask 

 where I have plenty of oxygen, the rich part of the atmos- 

 phere, and you now see that the smoke is all consumed. This 

 is the first part of our experiment; and now what follows? 

 The carbon which you saw flying off from the turpentine 

 flame in the air is now entirely burned in this oxygen, and 

 we shall find that it will, by this rough and temporary experi- 

 ment, give us exactly the same conclusion and result as we 

 had from the combustion of the candle. The reason why 

 I make the experiment in this manner is solely that I may 

 cause the steps of our demonstration to be so simple that you 

 can never for a moment lose the train of reasoning, if you 

 only pay attention. All the carbon which is burned in 

 oxygen, or air, comes out as carbonic acid, while those par- 

 ticles which are not so burned show you the second substance 

 in the carbonic acid, namely, the carbon that body which 

 made the flame so bright while there was plenty of air, but 

 which was thrown off in excess when there was not oxygen 

 enough to burn it. 



