38 THE EVOLUTION OF SCIENCE. 



according to the laws of mechanics to do a certain work, 

 is an instrument ; a new arrangement of ideas according 

 to the laws of thought to explain or to discover a truth 

 of nature, is an hypothesis. Both are inventions. More- 

 over, the last is of a higher order of invention than the 

 first. Newton and Watt were both inventors. Looked 

 at from a scientific standpoint, Newton was the greater 

 inventor of the two, inasmuch as Newton's theory of uni- 

 versal gravitation resulted from the combination of pure- 

 ly mental conceptions, while the steam engine of Watt 

 resulted from the contemplation of mechanical actions. 

 Likewise, as an element in the growth of science, the 

 invention of hypotheses outranks the invention of instru- 

 ments. The office of instruments is to establish facts ; 

 but facts are only the material out of which science is 

 constructed. Facts may constitute knowledge, but 

 knowledge must be suitably arranged and referred to 

 general principles in order to become science. The office 

 of an hypothesis is to group and explain the facts ; and 

 it is by the invention and improvement of hypotheses 

 that a chaotic accumulation of instrumental observations 

 is transformed into an organized system subject to gen- 

 eral principles. Look, for example, at meteorology. It 

 is the most chaotic of the sciences, notwithstanding the 

 fact that it is the science which "gives the description 

 and explanation of the phenomena on which weather and 

 climate depend." We may well suppose that it is not 

 from any lack of interest in the subject that the science 

 of weather has remained undeveloped. Nor is it from 

 any lack of instruments ; nor from any poverty of ob- 

 servations. There are thermometers which show atmos- 

 pheric changes in temperature to the fraction of a degree ; 

 barometers measuring changes in pressure down to the 

 five ten- thousandths of a pound to the square inch, and 

 instruments for the precise measure of moisture and elec- 

 tricity. 



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