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How then are those hidden things to be revealed ? 

 How, for example, are we to lay hold of the physical 

 basis of light, since, like that of life itself, it lies entirely 

 without the domain of the senses ? Now, philosophers 

 may be right in affirming that we cannot transcend ex- 

 perience. But we can, at all events, carry it a long way 

 from its origin. We can also magnify, diminish, qualify, 

 and combine experiences, so as to render them fit for 

 purposes entirely new. We are gifted with the power of 

 imagination, combining what the Germans called An- 

 schauiingsgabe and Einbildungskraft, and by this power 

 we can lighten the darkness which surrounds the world 

 of the senses. 



There are tories even in science who regard imagina- 

 tion as a faculty to be feared and avoided rather than 

 employed. They had observed its action in weak ves- 

 sels and were unduly impressed by its disasters. But 

 they might with equal justice point to exploded boilers 

 as an argument against the use of steam. Bounded and 

 conditioned by cooperant reason, imagination becomes 

 the mightiest instrument of the physical discoverer. 

 Newton's passage from a falling apple to a falling moon 

 was a leap of the imagination. When William Thom- 

 son tries to place the ultimate particles of matter be- 

 tween his compass points, and to apply to them a scale 

 of millimeters, it is an exercise of the imagination. 

 And in much that has been recently said about proto- 

 plasm and life, we have the outgoings of the imagination 

 guided and controlled by the known analogies of science. 

 In fact, without this power our knowledge of nature 

 would be a mere tabulation of coexistences and sequences. 

 We should still believe in the succession of day and 

 night, of summer and winter ; but the soul of force 



