ON THE PHYSICAL VIEW OF NATTKE. 



IL 



sutlicieully cleared up in ^luhr's sliurt aper^u, which dfyes 

 not attempt to distinguish between the two ditVerent 

 meanings of tlie word force, nor in the earlier papei-s 

 of Mayer, wliu, however, in later writings shows a clear 

 appreciation of the dilhculty. In Helmholtz's menujii-s 

 the desired clearness was only attained by mathenuitical 

 reasoning, which in his age and country was accessible 

 to but few naturalists. The second and probably the 

 fundamental obstacle in the way of a just recogni- 

 tion of the new truth lu}' in the fatal use of the term 

 " force " in two distinct meanings. Popularly tlie ditti- 

 culty has only been removed l>y the creation of a new 

 vocabulary, and dates from the introduction of the term 

 " work " by Clausius in 1850, and of the term " energy " 

 by William Thomson, who adopted it from Young in the ^^f '"'""" 

 year 1852. The confusion which had been kept up by '^'""'"''" 

 employing the word " force " to mean not only pressure 

 or dead force (in the Newtonian sense) but also acting 

 force {vis viva in the Leibnizian sense), and with this 

 confusion the whole meaning of the great controversies 

 which raged for many years between the Cartesians 

 and Leibnizians on the correct measure of force, was 

 then removed, and a grammatical and logical founda- 



15. 

 Work"anil 

 energy " 

 introluced 



from Mayer's published correspond- 

 ence that some remarks of Liel)ig 

 himself, which appeared early in 

 1842, induced him to send him his 

 first paper in order " not to lose the 

 right of j)riurity " (letter to Gries- 

 inger, fiili-Gth December 184"2, in 

 ' Schriften and Briefe,' ed. Wey- 

 rauch, p. 190). Mayer there says : 

 " Liebig wrote to me, inter alia: 

 ' As to what force, cause, and 

 effect are, there exist in general 



such confused notions that an 

 easily understood explanation must 

 be considered to V)e of real value.' 

 One would accordingly tliink tliat 

 he himself considers himself quite 

 above this general confusion ; that 

 this is ni>t so, 1 could see surti- 

 ciently from his ' phenomena of 

 motion in the animal organism ' 

 (Liebig, 'Die organische Chemie, 

 &c.; 1842, p. 183, &c.)" 



