EVOLUTION OF COLLOIDS 137 



telescope displays to the astronomer. A solar 

 system might be seen representing the mole- 

 cule, the sun and its attendant primary planets 

 would indicate the atoms, and the satellites 

 of the planets would stand for the electrons. 

 Closer examination under this imaginary 

 microscope might reveal that the sun and the 

 attendant planets, and their satellites, were, 

 as a whole, revolving in concert with other 

 suns and other solar systems, and this latter 

 motion would represent molecular affinity. 

 The variations in numbers in the various 

 systems in equipoise would stand for chemical 

 valency at each stage. Some planets would 

 have only one moon, others four, in a solar 

 system the number of planets might vary, 

 and in the constellations there might be 

 similar balances amongst the constituent 

 solar systems. 



It is, perchance, but an analogy, but it is 

 one which fittingly illustrates the facts of the 

 case. 



Water is not the only substance which forms 

 these molecular unions with crystalloids, 

 alcohol and other organic substances may 

 replace water of crystallization, or, apart 

 from water, different crystalloids which come 

 out of solution in the same crystalline form 

 can replace each other in the same crystal. 



