A HISTORY OF SCIENCE 



exertion, to vault almost to the house-tops if he lived 

 on a small planet like the moon ; but, on the other hand, 

 would be held prone by his own weight if transported 

 to a great planet like Jupiter. 



When, further, we reflect that with all our capacity 

 to measure and estimate this strange force of gravita- 

 tion we, after all, know absolutely nothing as to its 

 real nature ; that we cannot even imagine how one por- 

 tion of matter can act on another across an infinite 

 abysm (or, for that matter, across the smallest space), 

 we see at once that our most elementary scientific 

 studies bring us into the presence of inscrutable mys- 

 teries. In whatever direction we turn this view is but 

 emphasized. Electricity, magnetism, the hypothetical 

 ether, the inscrutable forces manifested everywhere in 

 the biological field all these are, as regard their ulti- 

 mate nature, altogether mysterious. 



In a word, the student of nature is dealing every- 

 where with the wonderful, the incomprehensible. Yet 

 all the manifestations that he observes are found to 

 repeat themselves in certain unvarying sequences. 

 Certain applications of energy will produce certain 

 movements of matter. We may not know the nature 

 of the so-called cause, but we learn to measure the re- 

 sult, and in other allied cases we learn to reason back 

 or infer the cause from observation of results. The 

 latter indeed is the essence of scientific inquiry. When 

 certain series of phenomena have been classified to- 

 gether as obviously occurring under the domination of 

 the same or similar causes, we speak of having de- 

 termined a law of nature. For example, the fact that 

 any body in motion tends to go on at the same rate of 



234 



