MOLECULES. 373 



When Lucretius wishes us to form a mental representation of the motion 

 of atoms, he tells us to look at a sunbeam shining through a darkened room 

 (the same instrument of research by which Dr Tyndall makes visible to us the 

 dust we breathe), and to observe the motes which chase each other in all 

 directions through it. This motion of the visible motes, he tells us, is but a 

 result of the far more complicated motion of the invisible atoms which knock 

 the motes about. In his dream of nature, as Tennyson tells us, he 



"Saw the flaring atom-streams 

 And torrents of her myriad universe, 

 Ruining along the illimitable inane, 

 Fly on. to clash together again, and make 

 Another and another frame of things 

 For ever." 



And it is no wonder that he should ,have attempted to burst the bonds of 

 Fate by making his atoms deviate from their courses at quite uncertain times 

 and places, thus attributing to them a kind of irrational free will, which on 

 his materialistic theory is the only explanation of that power of voluntary 

 action of which we ourselves are conscious. 



As long as we have to deal . with only two molecules, and have all the 

 data given us, we can calculate the result of their encounter ; but when we 

 have to deal with millions of molecules, each of which has millions of encounters 

 in a second, the complexity of the problem seems to shut out all hope of a 

 legitimate solution. 



The modern atomists have therefore adopted a method which is, I believe, 

 new in the department of mathematical physics, though it has long been in 

 use in the section of Statistics. When the working members of Section F get 

 hold of a report of the Census, or any other document containing the numerical 

 data of Economic and Social Science, they begin by distributing the whole 

 population into groups, according to age, income-tax, education, religious belief, 

 or criminal convictions. The number of individuals is far too great to allow of 

 their tracing the history of each separately, so that, in order to reduce their 

 labour within human limits, they concentrate their attention on a small number 

 of artificial groups. The varying number of individuals in each group, and not 

 the varying state of each individual, is the primary datum from which they work. 



This, of course, is not the only method of studying human nature. We 

 may observe the conduct of individual men and compare it with that conduct 



