DISCOVERY BY TESTING HYPOTHESES. 515 



Priestley, whilst making his great qualitative discoveries 

 in chemistry, was unable to make a quantitative chemical 

 analysis. In ancient times a very great number of dis- 

 coveries, especially in chemistry, were made whilst search- 

 ing for impossible things, such as perpetual motion in 

 physics, and the elixir vitse and philosopher's stone in 

 chemistry ; and we are probably even now, unknowingly, 

 pursuing a similar course, though to avery much less extent. 



But although a true hypothesis is not essential to dis- 

 covery, it is best when we do start upon an hypothesis 

 that it be a true one, because we then know better what 

 effect to look for, how best to make it conspicuous, and 

 better how to detect it if it is small in amount. A wrong- 

 hypothesis might also bias our minds, and thus make us 

 fail to notice the actual results. It is for these reasons 

 a 1 so a great advantage in research to possess truthful 

 ideas of the fundamental principles and laws of the 

 sciences. The greatest discoverers have usually possessed 

 the most truthful views of science. 



Not unfrequently an hypothesis 6r question is sug- 

 gested by one person, and tested by another. Thus 

 Adams was led to calculate the orbit of Neptune by 

 reading the following sentence, contained in Somerville's 

 'Connection of the Physical Sciences,' 6th edit., 1842 : 

 ' If, after the lapse of years, the tables, formed upon a 

 combination of 'numerous observations, should be still 

 inadequate to represent the motions of Uranus, the dis- 

 crepancies may reveal the existence, nay, even the mass 

 and orbit of a body placed for ever beyond the reach of 

 vision/ 



a. By searching for one thing and finding another. 

 As the whole of the knowledge or data necessary to 

 enable us to test a new hypothesis is rarely available, we 

 require, in nearly all such cases, to make new experiments 



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