112 FRAGMENTS OF SCIENCS 



tions. 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, ac- 

 companying and guiding all his experiments. His 

 strength and fertility as a discoverer is to be referred 

 in great part to the stimulus of his imagination. Scien- 

 tific men fight shy of the word because of its ultra- 

 scientific connotations; but the fact is, that, without the 

 exercise of this power, our knowledge of nature would 

 be a mere tabulation 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 disap- 

 pear, 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 afterward some of 

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

 us begin with the rudimentary experiences. Observe the 

 falling of heavy rain-drops into a tranquil pond. Each 

 drop as it strikes the water becomes a centre of disturb- 

 ance, from which a series of ring-ripples expand outward. 

 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 body plunged in the water, as the wave- 

 lets reach it in succession. But a finer motion is at the 

 same time set up and propagated. If the head and ears 

 be immersed in the water, as in an experiment of Frai:k- 



