462 On the Conservation of Force. [1858. 



heat, electricity, magnetism, chemical action and motion is a 

 familiar thought ; neither can I perceive any reason why they 

 should be led to exclude, a priori, the cause of gravitation 

 from association with the cause of these other phenomena re- 

 spectively. All that they are limited by in their various investiga- 

 tions, whatever directions they may take, is the necessity of 

 making no assumption directly contradictory of the conservation 

 of force applied to the sum of all the forces concerned, and to 

 endeavour to discover the different directions in which the 

 various parts of the total force have been exerted. 



Those who admit separate forces inter-unchangeable, have 

 to show that each of these forces is separately subject to the 

 principle of conservation. If gravitation be such a separate 

 force, and yet its power in the action of two particles be sup- 

 posed to be diminished fourfold by doubling the distance, surely 

 some new action, having true gravitation character, and that 

 alone, ought to appear ; for how else can the totality of the force 

 remain unchanged? To define the force as " a simple attractive 

 force exerted between any two or all the particles of matter, 

 with a strength varying inversely as the square of the distance," 

 is not to answer the question; nor does it indicate or even 

 assume what are the other complementary results which occur ; 

 or allow the supposition that such are necessary: it is simply, 

 as it appears to me, to deny the conservation of force. 



As to the gravitating force, I do not presume to say that I 

 have the least idea of what occurs in two particles when their 

 power of mutually approaching each other is changed by 

 their being placed at different distances ; but I have a strong 

 conviction, through the influence on my mind of the doctrine 

 of conservation, that there is a change ; and that the phe- 

 nomena resulting from the change will probably appear some 

 day as the result of careful research. If it be said that 

 " 'twere to consider too curiously to consider so," then I must 

 dissent. To refrain to consider, would be to ignore the principle 

 of the conservation of force, and to stop the inquiry which it 

 suggests : whereas to admit the proper logical force of the 

 principle in our hypotheses and considerations, and to permit 

 its guidance in a cautious yet courageous course of investi- 

 gation, may give us power to enlarge the generalities we already 

 possess in respect of heat, motion, electricity, magnetism, &c. ; 



