in.] IDEAL GENESIS OF MATTER 243 



machines. Unquestionably, too, the terms in which 

 Clausius generalized it were mathematical, and a cal- 

 culable magnitude, "entropy," was, in fact, the final 

 conception to which he was led. Such precision is necessary 

 for practical applications. But the law might have been 

 vaguely conceived, and, if absolutely necessary, it might 

 have been roughly formulated, even though no one had 

 ever thought of measuring the different energies of the 

 physical world, even though the concept of energy had 

 not been created. Essentially, it expresses the fact that 

 all physical changes have a tendency to be degraded into 

 heat, and that heat tends to be distributed among bodies 

 in a uniform manner. In this less precise form, it becomes 

 independent of any convention; it is the most metaphysi- 

 cal of the laws of physics since it points out without inter- 

 posed symbols, without artificial devices of measurements, 

 the direction in which the world is going. It tells us that 

 changes that are visible and heterogeneous will be more and 

 more diluted into changes that are invisible and homo- 

 geneous, and that the instability to which we owe the rich- 

 ness and variety of the changes taking place in our solar 

 system will gradually give way to the relative stability 

 of elementary vibrations continually and perpetually 

 repeated. Just so with a man who keeps up his strength 

 as he grows old, but spends it less and less in actions, and 

 comes, in the end, to employ it entirely in making his lungs 

 breathe and his heart beat. 



From this point of view, a world like our solar system 

 is seen to be ever exhausting something of the muta- 

 bility it contains. In the beginning, it had the maximum of 

 possible utilization of energy: this mutability has gone 

 on diminishing unceasingly. Whence does it come? We 

 might at first suppose that it has come from some other 

 point of space, but the difficulty is only set back, and for 



