450 On the Conservation of Force. [1857. 



suggest or deal with any of the consequences of the changed 

 part or condition of the force, and cannot tell whether they 

 depend on, or are related to, conditions external or internal to 

 the gravitating particle ; and, as it appears to me, can say 

 neither yes nor no to any of the arguments or probabilities 

 belonging to the subject. 



If the definition denies the occurrence of such contingent re- 

 sults, it seems to me to be unphilosophical ; if it simply ignores 

 them, I think it is imperfect and insufficient ; if it admits these 

 things, or any part of them, then it prepares the natural phi- 

 losopher to look for effects and conditions as yet unknown, and 

 is open to any degree of development of the consequences and 

 relations of power : by denying, it opposes a dogmatic barrier 

 to improvement ; by ignoring, it becomes in many respects an 

 inert thing, often much in the way ; by admitting, it rises to the 

 dignity of a stimulus to investigation, a pilot to human science. 

 The principle of the conservation of force would lead us to 

 assume, that when A and B attract each other less because of 

 increasing distance, then some other exertion of power, either 

 within or without them, is proportionately growing up ; and 

 again, that when their distance is diminished, as from 10 to 

 1, the power of attraction, now increased a hundred-fold, 

 has been produced out of some other form of power which has 

 been equivalently reduced. This enlarged assumption of the 

 nature of gravity is not more metaphysical than the half as- 

 sumption ; and is, I believe, more philosophical, and more in 

 accordance with all physical considerations. The half assump- 

 tion is, in my view of the matter, more dogmatic and irrational 

 than the whole, because it leaves it to be understood that 

 power can be created and destroyed almost at pleasure. 



When the equivalents of the various forms of force, as far 

 as they are known, are considered, their differences appear 

 very great ; thus, a grain of water is known to have electric 

 relations equivalent to a very powerful flash of lightning. It 

 may therefore be supposed that a very large apparent amount 

 of the force causing the phenomena of gravitation, may be the 

 equivalent of a very small change in some unknown condition 

 of the bodies, whose attraction is varying by change of distance. 

 For my own part, many considerations urge my mind towards 

 the idea of a cause of gravity, which is not resident in the par- 



