418 Prof. R. Clausius on the Second Fundamental 



it must be observed that we may regard the word "heat" as 

 also including light ; and the conception of " ergon '* is very 

 much more comprehensive still. Cliemical action, the effects of 

 electrical and magnetic forces, the production and cessation of 

 motion, whether it be the progressive, rotatory, or vibratory mo- 

 tion of ponderable masses, or whether it be the motion of elec- 

 tricity, may all, so far as they are here considered, be represented 

 as ergon. We are consequently dealing with a theorem that 

 applies to all natural phenomena. 



Helmholtz, who at once recognized this general significance 

 of the theorem, and established it clearly and convincingly in his 

 beautiful essay on this subject by applying the theorem to the 

 various branches of physics, o-ave to the theorem, when thus ex- 

 tended as widely as possible, ,he name of the Theorem of the 

 Conservation of Force, for which it would perhaps be a little 

 better still to say the Theorem of the Conservation of Energy. 



When the object is to make it express a general fundamental 

 law of the universe, this theorem may be put into some such 

 form as the following: — One form of Energy can be transformed 

 into another form of Energy, but the quantity of Energy is thereby 

 never diminished; on the contrary, the total amount of Energy ex- 

 isting in the universe remains just as constant as the total amount 

 of Matter in the universe. 



Notwithstanding that the truth of this theorem is beyond a 

 doubt, and that it expresses the unchangeableness of the uni- 

 verse m a certain very important respect, we should yet be going 

 too far were we to assume that it affords a confirmation of the 

 view according to which the whole condition of the universe is 

 represented as unchangeable, and all involved in never-ending 

 cycles. The second fundamental theorem of the mechanical 

 theory of heat contradicts this view most distinctly. 



As was said above, the common rule holds good for all the 

 endlessly manifold changes which go on in the world, that trans- 

 formations in opposite directions do not necessarily occur in equal 

 numbers, but that the difference can only be on one determi- 

 nate side, namely, so that the positive transformations prepon- 

 derate over the negative. Hence it follows that the condition of 

 the universe must gradually change more and more in a certain 

 particular direction. 



The ergon which the forces of nature are capable of perform- 

 ing, and which is contained in the existing motions of the bodies 

 which make up the system of the universe, will be gradually 

 converted more and more into heat. The heat, inasmuch as it 

 always tends to pass from hotter to colder bodies, and so to 

 equalize existing differences of temperature, will gradually ac- 

 quire a more and more uniform distribution, and a certain equi- 



