512 Dr. J. R. Mayer on the Mechanical Equivalent of Heat. 



with confirmation, wc apply an equalizing process, and take away 

 the word "force" from the connexion in which it is superfluous 

 and hurtful, and bring it to where wc are in want of it, we get 

 rid at one time of two important obstacles. The higher mathe- 

 matics at once cease to be required in order to gain admittance 

 into the theory of motion : nature presents herself in simple 

 beauty before the astonished eye, and even the less gifted may 

 now behold many things which hitherto were concealed from 

 the most learned philosophers. 



Force and matter are indestructible objects. This law, to 

 which individual facts may most simply be referred, and which 

 therefore I might figuratively call the heliocentric stand-point, 

 constitutes a natural basis for physics, chemistry, physiology, 

 and philosophy. 



Among the facts which, though known, have been hitherto 

 only empirically established and have remained isolated, but 

 which can be easily referred to this natural law, is the one that 

 electric and magnetic attraction cannot be isolated any more than 

 gravity, or that the strength of this attraction undergoes no 

 alteration, so long as the distance remains the same, by the in- 

 tervening of indifferent substances (non-conductors). 



Among facts which have remained unknown up to the most 

 recent times, I will refer only to the influence which the ebb and 

 flow of the tide exerts, in accordance with the known laws of 

 mechanics, on the motion of the earth about its axis. * A fact of 

 such importance, standing, as it does, in close relation with the 

 fundamental law just stated, having been able to escape the atten- 

 tion of naturalists, is of itself a proof that the prevailing system 

 has no exclusive title. 



For the rest, it will not have escaped those who are acquainted 

 with the modern literature of science that a modification of scien- 

 tific language in the sense of my views is actually beginning to 

 take place. But in matters of this kind the chief part of the 

 work must be left to time. 



According to what has been said thus far, the vis viva of mo- 

 tion must be called a force. But since the expression vis viva 

 denotes in mechanics, not only a magnitude which is propor- 

 tional to the mass and to the square of its velocity, but also one 

 which is proportional to the mass and to the height from w T hich 

 it has fallen, force thus conceived naturally divides itself into two 

 very easily distinguished species, each of which requires a distinct 

 technical name, for which the words motion (Bewegung) and 

 falling-force (Fallkraft) seem to me the most appropriate*. 



[* The distinction here drawn between " motion " and " falling force " is 

 the same as that made by Helmholtz {Die Erhaltung der Kraft, 1847) be- 

 tween " vis viva " (lebendiye Kraft) and " tension " (Spankraft). The En- 



