122 HERMANN VON HELMHOLTZ 



this great law (to which he leads his audience by comparing 

 the development of energy in natural processes in relation 

 to its utility to man, with the driving energy of machines), 

 he proceeds to the question whether the total quantity of 

 working energy, which cannot be augmented without a corre- 

 sponding consumption, can be either lost or diminished, and 

 replies that ' it certainly can for the purposes of our machines, 

 but not for nature as a whole*. He then passes on to the 

 Carnot-Clausius law, according to which heat can only be 

 converted into mechanical work when it passes from a warmer 

 to a cooler body, even then its conversion is only partial, 

 so that we cannot transform the heat of any body that cannot 

 be further cooled into another form of energy, whether 

 mechanical, electrical, or chemical and develops the conse- 

 quences of this law of nature for the universe : ' these physico- 

 mechanical laws are, as it were, the telescopes of our spiritual 

 eye, and penetrate into the farthest night of past and future ' 

 thence deducing results which du Bois-Reymond aptly reckons 

 among his ' most brilliant discoveries '. 



If all bodies in nature had the same temperature, it would 

 be impossible to convert any portion of their heat into 

 mechanical work. The potential store of energy in the 

 universe can thus be divided into two portions, one of which 

 is heat and continues as such, while the other (to which 

 a portion of the heat of the warmer bodies, and the total 

 supply of chemical, electrical, and magnetic energy belong) 

 is the source of all the countless interacting changes in 

 Nature. Now since the heat of warmer bodies is perpetually 

 striving to pass into those that are cooler, so as to establish 

 an equilibrium of temperature, and since in every chemical 

 or electrical process, and at each motion of a terrestrial body 

 subject to collision or friction, a portion of the mechanical energy 

 passes into heat, of which a part only can be reconverted, 

 it follows that while the first portion of the store of energy 

 (the unaltered heat) increases constantly in every natural 

 process, the second portion, the mechanical, chemical, and 

 electrical energies, is constantly diminished. And thus, as 

 all the energy of the world must eventually be transformed 

 into heat, and all heat will attain an equilibrium of temperature, 

 there will come, as Lord Kelvin predicted, a total arrestation 



