286 E. G. Spaulding 



By a system may be understood two or more species of energy 

 coexisting within certain spatial limits. A system may, therefore, 

 even if it is not to be isolated, be limited in this spatial sense. 

 Accordingly, but only under certain conditions, which will be 

 subsequently stated, the process taking place within such a system 

 may consist in the change of a definite quantum of one energy- 

 form into that of another. This, then, is transformation, and 

 leads to the second statement of the principle of conservation. 



In all energy transformations the quantum of one form dis- 

 appearing reappears as a total, equal quantum of one or more 

 other forms. 



The First Law does not, however, state the condition for these 

 transformations. 



The Second Law does this. According to it, in its generalized 

 form, first, each species of energy is the product of two factors, 

 an extensity or capacity and an intensity or potential, these of 

 course being different in the different species. Second, it is in 

 virtue of intensities that events take place, but only under certain 

 conditions : An intensity is a gradient and has direction. Accord- 

 ingly, two intensities may be opposed, and meet, as it were, at 

 a common point. Under this condition, they must be either equal 

 or unequal. When the latter is the case there is, manifestly, a 

 difference of intensity or potential; and if no third intensity be 

 present, to supplement^ the lesser one and to "make up" this 

 difference, that is to "compensate" it, then something must occur; 

 an energy transfer will take place from the quantum of the higher 

 to that of the lower intensity. It is in this specific and exact form 

 that the principle of efficient physical causation appears, thus 

 giving us a "law of events." 



This may be stated: Granted that all events in nature are 

 energy transfers, for these the necessary condition is, not merely 

 that there "should be a difference between opposed intensities, but 

 there must be at the same time an uncompensated difference. 

 Then, with such an uncompensated potential difference existing, 

 the process of doing away with it is forthwith initiated and takes 



^Such supplementation is not additive. 



