54 FRA GMENTS OF SCIENCE. 



Thus pondering, and questioning, and striving to sup- 

 plement that which is felt and seen, but which is incom- 

 plete, 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 poten- 

 tial motion, of which all its phenomena are but special 

 forms. This motion manifests 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, nothing 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 

 derived. 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 will re- 

 spond. Change the pitch of your voice; the first string 

 ceases to vibrate, but another replies. Change again the 

 pitch; the first two strings are silent, while another re- 

 sounds. Thus is sentient man acted on by Nature, the 

 optic, the auditory and other nerves of the human body 

 being so many strings differently tuned, and responsive to 

 different forms of the universal power. 



CHAPTER III. 



ON RADIANT HEAT IN RELATION TO THE COLOR AND 

 CHEMICAL CONSTITUTION OF BODIES.* 



ONE OF the most important functions of physical science, 

 considered as a discipline of the mind, is to enable us by 

 means of the sensible processes of Nature to apprehend the 



* A discourse delivered in the Royal Institution of Great Britain, 

 Jan. 19, 1866. 



