CLASSES OF SCIENTIFIC FACTS. 85 



realm of new knowledge. An exceptional instance may 

 also be of great value by leading in a similar way to the 

 discovery of a great general truth. Residuary instances 

 are also sometimes of the greatest importance, and have 

 led to some of the greatest discoveries. 1 According to 

 Brewster, c a collection of facts, however skilfully they 

 may be conjured with, can never yield general laws 

 unless they contain that master-fact in which the dis- 

 covery resides, or upon which the law mainly depends.' 

 Extreme or conspicuous instances possess an extrinsic value 

 in consequence of their great fitness for the purposes of 

 illustration and experiment, and frequently also for practi- 

 cal use in inventions and technical operations. And new 

 facts have a special value in exciting attention due to 

 their novelty alone ; novelty is the charm of ' news.' 

 Different facts also have very different degrees of com- 

 plexity. Thus, the statement ' I am well ' is a far more 

 complex one, and includes a much larger number of phe- 

 nomena than the one ' Lead is heavy.' 



As the basis of all science is facts, the first question 

 respecting any new statement or assertion in science is, is 

 it true ? is the so-called fact really a fact ? For instance, 

 if a chemist says he has artificially produced quinine or 

 diamonds, we at once ask, is the substance really quinine ? 

 are they really diamonds ? and were they really formed 

 artificially ? for until we know this by sufficient evidence, 

 we cannot safely reason respecting them. If such evidence 

 does not appear in a reasonable time, either by publication 

 of the process or by commercial production of the article, 

 we may reasonably conclude the statement to be doubtful ; 

 because scarcely anyone who has made a valuable discovery 

 would permanently abstain from reaping either the fame 



1 See Herschel's Discourse on Natural Philosophy, pp. 156-8. 



