54 FMA 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 IK 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 lioval Institution of Great Britain, 
Jan. 19, 1866. 
