460 On the Conservation of Force. [1858. 



to his dependence on the certainty of gravitation applied by the 

 balance, so may the physical philosopher expect to find the 

 greatest security and the utmost aid in the principle of the 

 conservation of force. All that we have that is good and safe, 

 as the steam-engine, the electric telegraph, &c., witness to that 

 principle, it would require a perpetual motion, a fire without 

 heat, heat without a source, action without reaction, cause 

 without effect, or effect without a cause, to displace it from its 

 rank as a law of nature. 



During the year that has passed since the publication of the 

 preceding views regarding gravitation, &c., I have come to the 

 knowledge of various observations upon them, some adverse, 

 others favourable ; these have given me no reason to change my 

 own mode of viewing the subject, but some of them make me 

 think that I have not stated the matter with sufficient precision. 

 The word " force " is understood by many to mean simply "the 

 tendency of a body to pass from one place to another," which 

 is equivalent, I suppose, to the phrase " mechanical force ; " 

 those who so restrain its meaning must have found my argument 

 very obscure. What I mean by the word " force," is the cause 

 of a physical action ; the source or sources of all possible 

 changes amongst the particles or materials of the universe. 



It seems to me that the idea of the conservation of force is 

 absolutely independent of any notion we may form of the nature 

 of force or its varieties, and is as sure and may be as firmly 

 held in the mind, as if we, instead of being very ignorant, 

 understood perfectly every point about the cause of force and 

 the varied effects it can produce. There may be perfectly 

 distinct and separate causes of what are called chemical actions, 

 or electrical actions, or gravitating actions, constituting so many 

 forces; but if the "conservation of force" is a good and true 

 principle, each of these forces must be subject to it : none can 

 vary in its absolute amount ; each must be definite at all times, 

 whether for a particle, or for all the particles in the universe ; 

 and the sum also of the three forces must be equally unchange- 

 able. Or, there may be but one cause for these three sets of 

 actions, and in place of three forces we may really have but one, 

 convertible in its manifestations ; then the proportions between 

 one set of actions and another, as the chemical and the electrical, 



