IO2 E. G. SPAULDING. 



quite as logical, though not as practical to interpret the two as 

 quantitatively different. To interpret as equal is therefore to base 

 the law of conservation on an assumption not proven, yet not 

 disproven. 1 



In the second place the law is based upon the impossibility of 

 a system's continuing to do work unless energy is received from 

 without. In this the assumption is implicitly contained that work 

 cannot be created ex niliilo. Were it possible, however, for a 

 system to receive from without the work (energy) which it itself 

 does, a perpetual motion would be possible. 



II. The second law prevents this. In every " Ausgleichung" 

 or transformation (Umgleichung) of energy, some heat is pro- 

 duced, only part of which at best is again available, for the reason 

 that it tends to " dissipate " ; it cannot pass from the body of the 

 lower to that of the higher potential (temperature) but only con- 

 versely. The entropy of the universe is accordingly said to 

 increase. This characteristic of heat energy is a special case of 

 a law (the second) valid for all the energies. Its meaning is that 

 all events have a definite direction. 



According to the first law then if one form of energy disappears 

 another form or forms held to be quantitatively equal to it must 

 appear. Energy may therefore be defined as that which in 

 changing conserves itself. Implicit in both the first and second 

 laws is the definition of it as that which does work, but that there 

 are objections to this is evident from the facts stated in the 

 second, that some energy in the form of heat with no difference 

 of potential (7~) cannot do work. 



III. The factors of energy. Already present though unre- 

 cognized in the early development of mechanics, but made ex- 

 plicit first in thermodynamics, and later extended to all forms of 

 energy is the view that each is made up of the product of two 

 factors, a potential or intensity, on the one hand, and an extensity 

 or capacity factor, on the other. In heat energy these factors 

 are respectively temperature and entropy Qj T (specific heat), in 

 kinetic energy f^and MV, in volume energy (gases and solutions) 



1 This procedure illustrates the necessary dogmatism of all science, and the superi- 

 ority of a pragmatic to a logical justification, a subject which will be treated at length 

 in another paper. 



