﻿12 DARBISHIRE, Mendelian and Biometric Theories. 



tain that it was walking across a picture of a field ; each 

 would be convinced that he was right and the other 

 wrong ; yet that both were right could be recognized by 

 any man able to use a magnifying lens. This leads us to 

 a third feature of the relation between our two classes, 

 (which results from the fact that our knowledge has 

 probably developed along those lines that our point of 

 view has made most valuable), namely, that in proportion 

 as our knowledge of the component units is small so is 

 our knowledge of the mass result great. 



To take an example of these two ways of looking at 

 things. The climate of a country or long period of time 

 is a mass- phenomenon : the particular climatic condition 

 of a certain day is referred to as the weather.* It is, though 

 it may be becoming less, impossible to predict the weather 

 with precision : but the nature of the climate of a given 

 country or long period of time is a matter of tolerable cer- 

 tainty. Yet the statement that the summer is warm does 

 not exclude the possibility of a frost in May. That our 

 practical knowledge of the elements is confined to the 

 climate is evident from the fact that, having procured, we 

 begin to put on warmer clothing at a certain period of 

 the year : but if our intelligence were so sharpened, or our 

 meteorological instruments so improved that we could 

 predict the exact state of the weather a fortnight in 

 advance, we should not procure the warmer raiment until 

 we knew that it would be needed. 



Another phenomenon which may be looked at from 

 these two points of view is that of the causation of heat : 



*"By climate we mean the sum total of the meteorological phenomena 

 that characterize the average condition of the atmosphere at any one place 

 on the earth's surface. That which we call weather is only one phase in the 

 succession of phenomena whose complete cycle, recurring with greater or 

 less uniformity every year, constitutes the climate of any locality." P. I.— J. 

 Ilann's " Handbook of Climatology," transl. by R. de C. Ward, 1903. 



