A PREAMBLE ON ENERGY 65 



matical artifices ; it is obvious that the law of conservation is 

 not necessarily invalidated. 



In the familiar sense available energy is the capacity for setting 

 up physical change — " for doing work." But it is familiar 

 experience that energy in this sense can " be expended." There- 

 fore it would appear that it is not conserved. But available 

 energy that disappears can always be accounted for : kinetic 

 energy may appear to be lost, but it may only pass into the 

 potential phase. Further, energy that is " expended " becomes 

 " unavailable " (see Section 22/) and can still be traced. There- 

 fore, again, the law of conservation is preserved. 



Clearly the " law " of conservation is of the nature of a stipula- 

 tion made by scientific method. No scientific result can possibly 

 invalidate it, since it is a necessary element of scientific method 

 itself. Thus dreams, hallucinations, phantasms, and perhaps 

 *' spooks " are " real while they last." But they cannot be 

 " reduced to order " ; they are a nuisance to physical science 

 and they are dismissed from the domain of physical research — 

 because they are not conserved. 



All the same the invalidity, in the most precise sense, of the 

 law of conservation does not apply to experimental biology — 

 in its present phase. Presently we shall see that, so far as we can 

 investigate the processes of organic functioning, using (as we still 

 must use) the instruments of nineteenth-century physics, the 

 classical laws hold good. Yet again, will that always be the 

 limitation of biology } 



22c. The Entropy-Law. This is the fundamental generaliz- 

 ation of science — it is notable that the physical-mathematical 

 revolution of the last twenty years has not shaken it in the least. 

 The law^ of conservation we may regard as a logical category 

 (just yet, at all events, for innate '' laws " of thought are, no doubt, 

 evolving just as bodily structure evolves). But the entropy-law 

 appears to crystallize our knowledge that comes from sensory data. 



It is so very general that we can approach it from various ways. 



22^. In all Energy-Transformations Available Energy 

 Disappears. Some energy-transformations are (in the experi- 

 mental sense) truly quantitative ones — that is, the energy of the 

 system, before the transformation occurred, is precisely measur- 

 able and is the same as the energy (also precisely measurable) 

 after the transformation occurred. 



F 



