COHESION 41 



baft; for you see, if I introduce one end of this glass tube 

 into the bubble, that it has the power of contracting so 

 powerfully as to force enough air through the tube to 

 blow out a light (Fie. 22) ; the light is blown out. And look ! 

 see how the bubble is disappearing see how it is getting 

 smaller and smaller. 



There are twenty other experiments I might show you to 

 illustrate this power of cohesion of the particles of liquids. 

 For instance, what would you propose to me if, having 

 lost the stopper out of this alcohol bottle, I should want 

 to close it speedily with something near at hand. Well, a 

 bit of paper would not do, but a piece of linen cloth would, 

 or some of this cotton wool which I have here. I will put a 

 tuft of it into the neck of the alcohol bottle, and you see, 



FIG. 22 



FIG. 23 



when I turn it upside down, that it is perfectly well stop- 

 pered so far as the alcohol is concerned; the air can pass 

 through, but the alcohol can not. And if I were to take 

 an oil vessel this plan would do equally well, for in former 

 times they used to send us oil from Italy in flasks stoppered 

 only with cotton wool (at the present time the cotton is put 

 in after the oil has arrived here, but formerly it used to be 

 sent so stoppered). Now if it were not for the particles 

 of liquid cohering together, this alcohol would run out; 

 and if I had time I could have shown you a vessel with 

 the top, bottom, and sides altogether formed like a sieve, and 

 yet it would hold water, owing to the cohesion. 



You have now seen that the solid water can become fluid 

 by the addition of heat, owing to this lessening the attractive 

 force between its particles, and yet you see that there is a 

 good deal of attractive force remaining behind. I want now 

 to take you another step beyond. We saw that if we con- 



