158 FARADAY 



shall get the combustion of the candle below sending its 

 results into the bottle above ; and we shall soon find that this 

 bottle contains not merely an air that is bad as regards the 

 combustion of a taper put into it, but having other 

 properties. 



Let me take a little quick-lime and pour some common 

 water on to it the commonest water will do. I will stir it a 

 moment, then pour it upon a piece of filtering paper in a 

 funnel, and we shall very quickly have a clear water pro- 

 ceeding to the bottle below, as I have here, I have plenty of 

 this water in another bottle, but nevertheless I should like to 

 use the lime-water that was prepared before you, so that you 

 may see what its uses are. If I take some of this beautiful 

 clear lime-water, and pour it into this jar which has collected 

 the air from the candle, you will see a change coming about. 

 Do you see that the water has become quite milky? Ob- 

 serve, that will not happen with air merely Here is a bot 

 tie filled with air; and if I put a little lime-water into it, 

 neither the oxygen nor the nitrogen, nor any thing else that 

 is in that quantity of air, will make any change in the lime- 

 water; it remains perfectly clear, and no shaking of that 

 quantity of lime-water with that quantity of air in its com- 

 mon state will cause any change; but if I take this bottle 

 with the lime-water and hold it so as to get the general 

 products of the candle in contact with it, in a very short time 

 we shall hav<* it milky; there is the chalk, consisting of the 

 lime which we used in making the lime-water, combined 

 with something- that came from the candle that other 

 product which we are in search of, and which I want to 

 tell you about today. This is a substance made visible to us 

 by its action, which is not the action of the lime-water either 

 upon the oxygen or upon the nitrogen, nor upon the water 

 itself, but it is something new to us from the candle. And 

 then we find this white powder, produced by the lime-water 

 and the vapor from the candle, appears to us very much like 

 whitening or chalk, and when examined it does prove to be 

 exactly the same substance as whitening or chalk. So we 

 are led, or have been led, to observe upon the various cir- 

 cumstances of this experiment, and to trace this production 

 of chalk to its various causes, to give us the true knowledge 



