INTRODUCTORY ii 



less insight into scientific method. Works like Darwin's 

 Origin of Species and Descent of Man, Lyell's Prijiciples of 

 Geology, Helmholtz's Sensations of Tofie, or GoXion's Natural 

 Inheritance, can be profitably read and largely under- 

 stood by those who are not specially trained in the several 

 branches of science with which these works deal.^ It may 

 need some patience in the interpretation of scientific terms, 

 in learning the language of science, but like most cases in 

 which a new language has to be learnt, the comparison of 

 passages in which the same word or term recurs, will soon 

 lead to a just appreciation of its true meaning. In the 

 matter of language the descriptive natural sciences such as 

 geology or biology are more easily accessible to the lay- 

 man than the exact sciences such as algebra or mechanics, 

 where the reasoning process must often be clothed in 

 mathematical symbols, the right interpretation of which 

 may require months, if not years, of study. To this dis- 

 tinction between the descriptive and exact sciences I 

 propose to return later, when we are dealing with the 

 classification of the sciences. 



I would not have the reader suppose that the mere 

 perusal of some standard scientific work will, in my opinion, 

 produce a scientific habit of mind. I only suggest that it 

 will give some insight into scientific method and some 

 appreciation of its value. Those who can devote persist- 

 ently some four or five hours a week to the conscientious 

 study of any one limited branch of science will achieve in 

 the space of a year or two much more than this. The 

 busy layman is not bound to seek about for some branch 

 which will give him useful facts for his profession or occu- 

 pation in life. It does not indeed matter for the purpose 

 we have now in view whether he seek to make himself 

 proficient in geology, or biology, or geometry, or mechanics, 

 or even history or folklore, if these be studied scientifically. 

 What is necessary is the thorongh knowledge of some 

 small group of facts, the recognition of their relationship 



■^ The list might be easily increased, for example by W. Harvey's Ana- 

 tomical Dissertation on the Motion of the Heart and Blood, and by Faraday's 

 Experimental Researches. 



