154 ON THE INTERACTION OF NATURAL FORCES. 



from that time forward would be condemned to a state of 

 eternal rest. 



These consequences of the law of Carnot are, of course, only 

 valid provided that the law, when sufficiently tested, proves to 

 be universally correct. In the meantime there is little prospect 

 of the law being proved incorrect. At all events, we must 

 admire the sagacity of Thomson, who, in the letters of a long- 

 known little mathematical formula which only speaks of the 

 heat, volume, and pressure of bodies, was able to discern con- 

 sequences which threatened the universe, though certainly after 

 an infinite period of time, with eternal death. 



I have already given you notice that our path lay through 

 a thorny and unrefreshing field of mathematico-mechanical 

 developments. We have now left this portion of our road 

 behind us. The general principle which I have sought to lay 

 before you has conducted us to a point from which our view is a 

 wide one; and aided by this principle, we can now at pleasure 

 regard this or the other side of the surrounding world according 

 as our interest in the matter leads us. A glance into the narrow 

 laboratory of the physicist, with its small appliances and com- 

 plicated abstractions, will not be so attractive as a glance at the 

 wide heaven above us, the clouds, the rivers, the woods, and the 

 living beings around us. While regarding the laws which have 

 been deduced from the physical processes of terrestrial bodies as 

 applicable also to the heavenly bodies, let me remind you that 

 the same force which, acting at the earth's surface, we call 

 gravity (Schwere), acts as gravitation in the celestial spaces, and 

 also manifests its power in the motion of the immeasurably 

 distant double stars, which are governed by exactly the same 

 laws as those subsisting between the earth and moon; that 

 therefore the light and heat of terrestrial bodies do not in any 

 way differ essentially from those of the sun or of the most dis- 

 tant fixed star ; that the meteoric stones which sometimes fall 

 from external space upon the earth are composed of exactly the 

 same simple chemical substances as those with which we are 

 acquainted. We need, therefore, feel no scruple in granting that 

 general laws to which all terrestrial natural processes are subject 



