''SOME UNRECOGNIZED LAWS OF NATURES 779 



ing of inertia as if it were a " property " of matter, and tiie use 

 made of it in current mechanics, has long seemed to us mischiev- 

 ous. The present authors modify this law to read, " All matter 

 tends to persevere in whatever state it may happen to be and to 

 resist change/' In this form the law is more catholic. By per- 

 sistence the authors mean " the tendency of all matter to remain 

 in any given state, even after the conditions are altered (i. e., a 

 quality), while the term resistance is used to denote the intensity 

 of this persistence (i. e., a quantity)." The gain is not simply one 

 of terminology. It is a real gain, since it allows us to substitute 

 a simple idea, that of relative persistence or resistance, for the 

 somewhat complex and dissimilar ideas represented by such 

 terms as impact, inertia, latency, conductivity, charge, etc. 



The principle of reciprocity is founded on another dictum of 

 Newton's, that " all reactions are mutual and are directed to con- 

 trary parts." This means very simply that every change involves 

 at least two bodies, and that no body acts upon another, but 

 rather that two or more bodies react luith one another. This fol- 

 lows, indeed, from the principle of persistence. Since a change 

 of state in any body can be brought about by external agencies 

 only, it must follow that the jjersistence of this body can only be 

 overcome by the expenditure of a certain amount of resistance 

 on the part of the second or reacting body, and a corresponding 

 change in its own state. 



The two corollaries growing out of this law are also very 

 important : 



" 1. Bodies can react with each other only when there is a 

 difference of state in respect of any quality or tendency ; and 



" 3. The extent or intensity of the reaction will be propor- 

 tional to this difference, and will cease altogether when relative 

 equalization has been reached." 



This second corollary really involves the fourth primary prin- 

 ciple, that of equalization, in virtue of which all bodies tend to 

 come to a common state, and the drama of the universe, the 

 flux and flow of things, goes on eternally. It might at first seem 

 that with the operation of this principle of equalization the uni- 

 verse would at last, like a spent clock, run down and stop. Such 

 a view has indeed found expression in that modern and now 

 famous doctrine, the dissipation of energy. A universe com- 

 pletely run down, a dead uniformity of condition, are among the 

 striking spectacles of modern scientific speculation. It is not 

 that we see any loss of action in the cosmic drama. On the con- 

 trary, it goes on unceasingly. It is only that a limited concep- 

 tion of the principle of equalization requires such ultimate uni- 

 formity. But there is another element that must needs be taken 

 into consideration. The establishment of relative equilibrium 



