104 FKAGMENTS OF SCIENCE. 



steam. With accurate experiment and observation to 

 work upon. Imagination becomes the architect of 

 physical theory. Newton's passage from a falling apple 

 to a falling moon was an act of the prepared imagina- 

 tion, without which the ' laws of Kepler ' could never 

 have been traced to their foundations. Out of the facts 

 of chemistry the constructive imagination of Dalton 

 formed the atomic theory. Davy was richly endowed 

 with the imaginative faculty, while with Faraday its 

 exercise was incessant, preceding, accompanying and 

 guiding all his experiments. His strength and fertil- 

 ity as a discoverer is to be referred in great part to 

 the stimulus of his imagination. Scientific men fight 

 shy of the word because of its ultra-scientific connota- 

 tions; but the fact is that without the exercise of this 

 power, our knowledge of nature would be a mere tabu- 

 lation of co-existences and sequences. We should still 

 believe in the succession of day and night, of summer 

 and winter; but the conception of Force would vanish 

 from our universe; causal relations would disappear, 

 and with them that science which is now binding the 

 parts of nature to an organic whole. 



I should like to illustrate by a few simple instances 

 the use that scientific men have already made of this 

 power of imagination, and to indicate afterwards some 

 of the further uses that they are likely to make of it. 

 Let us begin with the rudimentary experiences. Ob- 

 serve the falling of heavy rain-drops into a tranquil 

 pond. Each drop as it strikes the water becomes a 

 centre of disturbance, from which a series of ring- 

 ripples expand outwards. Gravity and inertia are the 

 agents by which this wave-motion is produced, and a 

 rough experiment will suffice to show that the rate of 

 propagation does not amount to a foot a second. A 

 series of slight mechanical shocks is experienced by a 



