532 THE PRINCIPLES OF SCIENCE. [CHAP. 



account. This story, however, has been shown to be a 

 fabrication, the fact being that Simpson had for many 

 years been endeavouring to discover a better anaesthetic 

 than those previously employed, and that he tested the 

 properties of chloroform, among other substances, at the 

 suggestion of Waldie, a Liverpool chemist. The valuable 

 powers of chloral hydrate have since been discovered in 

 a like manner, and systematic inquiries are continually 

 being made into the therapeutic or economic values of 

 new chemical compounds. 



If we must attempt to draw a conclusion concerning 

 the part which chance plays in scientific discovery, it 

 must be allowed that it more or less affects the success of 

 all inductive investigation, but becomes less important 

 with the progress of science. Accident may bring a new 

 and valuable combination to the notice of some person who 

 had never expressly searched for a discovery of the kind, 

 and the probabilities are certainly in favour of a discovery 

 being occasionally made in this manner. But the greater 

 the tact and industry with which a physicist applies him- 

 self to the study of nature, the greater is the probability 

 that he will meet with fortunate accidents, and will turn 

 them to good account. Thus it comes to pass that, in the 

 refined investigations of the present day, genius united to 

 extensive knowledge, cultivated powers, and indomitable 

 industry, constitute the characteristics of the successful 

 discoverer. 



Empirical Observations subsequently Explained. 



The second great portion of scientific knowledge consists 

 of facts which have been first learnt in a purely empirical 

 manner, but have afterwards been shown to follow from 

 some law of nature, that is, from some highly probable 

 hypothesis. Facts are said to be explained when they are 

 thus brought into harmony with other facts, or bodies of 

 general knowledge. There are few words more familiarly 

 used in scientific phraseology than this word explanation, 

 and it is necessary to decide exactly what we mean by it, 

 since the question touches the deepest points concerning 

 the nature of science. Like most terms referring to men- 

 tal actions, the verbs to explain, or to explicate, involve 



