THE SIZE OF ATOMS. 217 



dimensions of a molecule of air are something 

 like that which I have stated. 



The four lines of argument which I have now 

 indicated lead all to substantially the same 

 estimate of the dimensions of molecular structure. 

 Jointly they establish, with what we cannot 

 but regard as a very high degree of probability, 

 the conclusion that, in any ordinary liquid, 

 transparent solid, or seemingly opaque solid, 

 the mean distance between the centres of 

 contiguous molecules is less than the i/5,ooo,oooth, 

 and greater than the i/i,ooo,ooo,oooth of a 

 centimetre. 



To form some conception of the degree of 

 coarse-grainedness indicated by this conclusion, 

 imagine a globe of water or glass, as large as 

 a football, 1 to be magnified up to the size of 

 the earth, each constituent molecule being 

 magnified in the same proportion. The magnified 

 structure would be more coarse-grained than a 

 heap of small shot, but probably less coarse- 

 grained than a heap of footballs. 



1 Or say a globe of 16 centimetres diameter. 



