﻿14 DARBISHIRE, Mendelian and Biometric Theories. 



whose attributes are still as essentially finite as our own, 

 would be able to do what is at present impossible 

 to us. For we have seen that the molecules in a 

 vessel of air at uniform temperature are moving with 

 velocities by no means uniform, though the mean velo- 

 city of any great number of them, arbitrarily selected, is 

 almost exactly uniform. Now let us suppose that such 

 a vessel is divided into two portions, A and B, by a 

 division in which there is a small hole, and that a being 

 who can see the individual molecules, opens and closes 

 this hole, so as to allow only the swifter molecules to pass 

 from A to B ; and only the slower ones to pass from B to 

 A. He will thus without expenditure of work, raise the 

 temperature of B and lower that of A, in contradiction to 

 the second law of thermo-dynamics." 



The point of view of the demon is so different from 

 that of the physicist that one of the truest generalizations 

 of the latter would be declared absolutely false by the 

 former : yet no one remains blind for a moment to the 

 fact that the contradiction of their respective statements 

 is only apparent, and is due to the radical difference in 

 their points of view. 



Now I believe that the difference between the point 

 of view of the Mendelian and the biometrician is very 

 like the difference between that of the demon and that 

 of the physicist. The biometrician, with a new weapon 

 of observation, is only concerned with mass pheno- 

 mena ; the individuals which go to swell his correlation 

 tables are, like the atoms of the physicist, units of 

 which no knowledge is required to attain the result 

 at which he aims. But I need not dwell on the exactness 

 of the parallel when we have these words from "the inven- 

 tor of the term biometry*": — "fOur knowledge of atoms 



* Nature. Oct. 27, 1904. P. 626. 



t Karl Pearson. "Grammar of Science, " 2nd Ed. v pp. 500 and 501. 



