Prof. Helmholtz on the Interaction of Natural Forces. 503 



at an end, and the complete cessation of all natural processes 

 must set in. The life of men, animals, and plants, could not of 

 course continue if the sun had lost his high temperature, and 

 with it his light, — if all the components of the earth^s sm-face 

 had closed those combinations which their affinities demand. In 

 short, the universe 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 mean time 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 conse- 

 quences 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 unrefreshiug field of mathematico-mechanical de- 

 velopments. We have now left this portion of our road behind 

 us. The general pi'inciple 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 there- 

 fore the light and heat of terrestrial bodies do not in any way 

 differ essentially from those of the sun, or of the most distant 

 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, are also 

 valid for other bodies than the earth. We will therefore make 

 use of our law to glance over the household of the universe with 

 respect to the store of force, capable of action, which it possesses. 



A number of singular peculiarities in the structure of our 



