and on the Conservation of Force. 167 



ledge 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 ai'gument 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 

 eflfects 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 unchangeable. 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 px'oportions between one set of 

 actions and another, as the chemical and the electi-ical, may be- 

 come very variable, so as to be utterly inconsistent with the 

 idea of the conservation of two separate forces (the electrical 

 and the chemical), but perfectly consistent with the conservation 

 of a force, being the common cause of the two or more sets of 

 action. 



It is perfectly true that we cannot always trace a force by its 

 actions, though we admit its conservation. Oxygen and hy- 

 drogen may remain mixed for years without showing any signs 

 of chemical activity ; they may be made at any given instant to 

 exhibit active results, and then assume a new state, in which 

 again they appear as passive bodies. Now, though we cannot 

 clearly explain what the chemical force is doing, that is to say, 

 what are its effects during the three periods before, at, and after 

 the active combination, and only by very vague assumption can 

 approach to a feeble conception of its respective states, yet we 

 do not bnp|)Ose the creation of a new portion of force for the 

 active moment of time, or the less beheve that the forces be- 

 longing to the oxygen and hydrogen exist unchanged in their 



