37-i M. J. R. Mayer on the Forces of Inorganic Nature, 



ceived causal relation. If gravity be called a force, a cause is 

 supposed which produces effects without itself diminishing, and 

 incorrect conceptions of the causal connexion of things are thereby 

 fostered. In order that a body may fall, it is no less necessary 

 that it should be lifted up, than that it should be heavy or possess 

 gravity ; the fall of bodies ought not therefore to be ascribed to 

 their gravity alone. 



It is the problem of Mechanics to develope the equations which 

 subsist between falling force and motion, motion and falling 

 force, and between different motions : here we will call to mind 

 only one point. The magnitude of the falling force v is directly 

 proportional (the earth's radius being assumed =00) to the 

 magnitude of the mass m, and the height d to which it is raised ; 

 that is, v = md. If the height d=\, to which the mass mis 

 raised, is transformed into the final velocity c=l of this mass, 

 we have also v = mc, but from the known relations existing 

 between d and c, it results that, for other values of d or of c, the 

 measure of the force v is toic 2 ; accordingly v = md=mc 9 : the law 

 of the conservation of vis viva is thus found to be based on the 

 general law of the indestructibility of causes. 



In numberless cases we see motion cease without having caused 

 another motion or the lifting of a weight ; but a force once in 

 existence cannot be annihilated, it can only change its form ; and 

 the question therefore arises, What other forms is force, which 

 we have become acquainted with as falling force and motion, 

 capable of assuming? Experience alone can lead us to a con- 

 clusion on this point. In order to experiment with advantage, 

 we must select implements which, besides causing a real cessa- 

 tion of motion, are as little as possible altered by the objects to 

 be examined. If, for example, we rub together two metal plates, 

 we see motion disappear, and heat, on the other hand, make its 

 appearance, and we have now only to ask whether motion is the 

 cause of heat. In order to come to a decision on this point, we 

 must discuss the question whether, in the numberless cases in 

 which the expenditure of motion is accompanied by the appear- 

 ance of heat, the motion has not some other effect than the pro- 

 duction of heat, and the heat some other cause than the motion. 



An attempt to ascertain the effects of ceasing motion has never 

 yet been seriously made ; without, therefore, wishing to exclude 

 a priori the hypotheses which it may be possible to set up, we 

 observe only that, as a rule, this effect cannot be supposed to be 

 an alteration in the state of aggregation of the moved (that is, 

 rubbing, &c.) bodies. If we assume that a certain quantity of 

 motion v is expended in the conversion of a rubbing substance 

 m into to,' we must then have m-\-v — n, andTO=?ro + ?;; and when 

 to is reconverted into m, v must appear again in some form or 



