72 FKAGMENTS OF SCIENCE. 



The outward facts of nature are insufficient to satisfy 

 the mind. We cannot be content with knowing that 

 the light and heat of the sun illuminate and warm the 

 world. We are led irresistibly to enquire, 'What is 

 light, and what is heat? ' and this question leads us at 

 once out of the region of sense into that of imagination.* 

 Thus pondering, and questioning, and striving to 

 supplement that which is felt and seen, but which is 

 incomplete, by something unfelt and unseen which is 

 necessary to its completeness, men of genius have in 

 part discerned, not only the nature of light and heat, 

 but also, through them, the general relationship of 

 natural phenomena. The working power of Nature 

 consists of actual or potential motion, of which all its 

 phenomena are but special forms. This motion mani- 

 fests itself in tangible and in intangible matter, being 

 incessantly transferred from the one to the other, and 

 incessantly transformed by the change. It is as real 

 in the waves of the ether as in the waves of the sea; 

 the latter derived as they are from winds, which in 

 their turn are derived from the sun are, indeed, noth- 

 ing more than the heaped-up motion of the ether waves. 

 It is the calorific waves emitted by the sun which heat 

 our air, produce our winds, and hence agitate our ocean. 

 And whether they break in foam upon the shore, or 

 rub silently against the ocean's bed, or subside by the 

 mutual friction of their own parts, the sea waves, which 

 cannot subside without producing heat, finally resolve 

 themselves into waves of ether, thus regenerating the 

 motion from which their temporary existence was de- 

 rived. This connection is typical. Nature is not an 

 aggregate of independent parts, but an organic whole. 

 If you open a piano and sing into it, a certain string 



* This line of thought was pursued further five years subse- 

 quently. See ' Scientific Use of the Imagination ' in Vol. II. 



