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FARADAY 



a soap-bubble, which of course will be filled with ail 

 and let it fall into this jar of carbonic acid it wik 

 float. But I shall first of all take one of these little 

 balloons filled with air. I am riot quite 1 sure where the 

 carbonic acid is; we will just try the depth, and see where- 

 abouts is its level. There, you see, we have this bladder 



FIG. 85 



floating on the carbonic acid ; and if I evolve some more of 

 the carbonic acid, the bladder will be lifted up higher. 

 There it goes; the jar is nearly full, and now I will see 

 whether I can blow a soap-bubble on that and float it in the 

 same way. [The lecturer here blew a soap-bubble and 

 allowed it to fall into the jar of carbonic acid, when it 

 floated in it midway.] It is floating as the balloon floated 

 by virtue of the greater weight of the carbonic acid than of 

 the air. And now, having so far given you the history of 

 the carbonic acid, as to its sources in the candle, as to its 

 physical properties and weight, when we next meet I shall 

 show you of what it is composed, and where it gets its ele- 

 ments from. 



