WHAT THIS WORLD IS MADE OF 



it is impossible to say, for the limits of the micro- 

 scope are reached with objects at least five hun- 

 dred times as large. And any experimental evi- 

 dence seems lacking. But Lord Rayleigh was able 

 to show that his oil-layer is continuous, because if it 

 had not been it would have arrested the movements 

 of some of the camphor particles, but not of all. It 

 stopped them all, so that either his or Professor 

 Rontgen's oil-layers may be taken as the extreme 

 limit of continuity at present attainable. 



So far we have been dealing only with substances 

 which give an apparently continuous surface. But 

 this is far from representing the extreme divisibility 

 of matter. The exploding soap-bubble disappears 

 in the air, and in the air vapors of oil or of water 

 exist in so finely divided a state that they cease to 

 sink under the force of gravity. They are drawn 

 up, or rather dissolved, in the air under the molec- 

 ular attraction of the air-particles. 



This process of dissolution, or breaking -up of 

 matter, is illustrated when we put sugar in the 

 coffee or the housewife adds bluing to the tub. It 

 is carried much further when we first dissolve a 

 little indigo in sulphuric acid, and then put this in 

 water. Thus treated, a single grain of indigo, the 

 weight, say, of a small pin, gives a distinct colora- 

 tion to a ton of water. In order to produce this 

 reaction, the indigo must have been divided up 



in 



