Io2 ANNUAL OF SCIENTIFIC DISCOVERY. 



Since the first publication of certain opinions respecting gravitation, etc., 

 I have come to the knowledge of various observations upon them, some 

 ii> I verse, others favorable: 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 under- 

 stood 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 in- 

 dependent 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 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 pro- 

 portions between one set of actions and another, as the chemical and the elec- 

 trical, may become 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 com- 

 mon cause of 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 hydrogen 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 combi- 

 nation, and only by very vague assumption can approach to a feeble concep- 

 tion of its respective states, yet we do not suppose the creation of a new 

 portion of force for the active moment of time, or the less believe that the 

 forces belonging to the oxygen and hydrogen exist unchanged in their 

 amount at all these periods, though varying in their results. A part may at 

 the active moment be thrown off as mechanical force, a part as radiant force, 

 a part disposed of we know not how; but believing, by the principle of con- 

 servation, that it is not increased or destroyed, our thoughts are directed to 

 search out what, at all and every period, it is doing, and how it is to be recog- 

 nized and measured. A problem, founded on the physical truth of nature, 

 is stated, and, being stated, is on the way to its solution. 



Those who admit the possibility of the common origin of all physical 

 force, and also acknowledge the principle of conservation, apply that princi- 

 ple to the sum total of the force. Though the amount of mechanical force 

 (using habitual language for convenience' sake) may remain unchanged 

 and definite iu its character lor a long time, yet when, as in the collision of 



