156 FARADAY 



talking more than I ought to do to make the experiment 

 succeed. 



[The lecturer here tried the experiment, and succeeded in 

 blowing the egg from one egg-cup to the other.] 



You see that the air which I blow goes downward between 

 the egg and the cup, and makes a blast under the egg, and 

 is thus able to lift a heavy thing; for a full egg is a very 

 heavy thing for air to lift. If you want to make the experi- 

 ment, you had better boil the egg quite hard first, and then 

 you may very safely try to blow it from one cup to the 

 other with a little care. 



I have now kept you long enough upon this property of 

 the weight of the air, but there is another thing I should like 

 to mention. You saw the way in which, in this popgun, I 

 was able to drive the second piece of potato half or two 

 thirds of an inch before the first piece started, by virtue of 

 the elasticity of the air, just as I pressed into the copper 

 bottle the particles of air by means of the pump. Now this 

 depends upon a wonderful property in the air, namely, its 

 elasticity, and I should like to give you a good illustration 

 of this. If I take any thing that confines the air properly, 

 as this membrane, which also is able to contract and expand 

 so as to give us a measure of the elasticity of the air, and 

 confine in this bladder a certain portion of air ; and then, if 

 we take the atmosphere off from the outside of it, just as in 

 these cases we put the pressure on if we take the pressure 

 off, you will see how it will then go on expanding and ex- 

 panding, larger and larger, until it will fill the whole of this 

 bell-jar, showing you that wonderful property of the air, its 

 elasticity, its compressibility, and expansibility, to an exceed- 

 ingly large extent, and which is very essential for the pur- 

 poses and services it performs in the economy of creation. 



We will now turn to another very important part of our 

 subject, remembering that we have examined the candle in 

 its burning, , and have found that it gives rise to various 

 products. We have the products, you know, of soot, of 

 water, and of something else, which you have not yet exam- 

 ined. We have collected the water, but have allowed the 

 other things to go into the air. Let us now examine some 

 of these other products. 



