ON THE PHYSICAL VIEW OF NATURE. 



115 



sufficiently cleared up in Mohr's short apergu, which does 

 not attempt to distinguish between the two different 

 meanings of the word force, nor in the earlier papers 

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

 appreciation of the difficulty. In Helmholtz's memoirs 

 the desired clearness was only attained by mathematical 

 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 lay in the fatal use of the term 

 " force " in two distinct meanings. Popularly the diffi- 

 culty has only been removed by the creation of a new 

 vocabulary, and dates from the introduction of the term 15. 

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



J introduced 



by William Thomson, who adopted it from Young in the ]^ d ciausiu8 

 year 1852. The confusion which had been kept up by ' Shomson - 

 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- 



from Mayer's published correspond- 

 ence that some remarks of Liebig 

 himself, which appeared early in 

 1842, induced him to send him his 

 first paper in order " not to lose the 

 right of priority " (letter to Gries- 

 inger, 5th-6th December 1842, in 

 ' Schriften und 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 be of real value.' 

 One would accordingly think that 

 lie himself considers himself quite 

 above this general confusion ; that 

 this is not so, I could see suffi- 

 ciently from his ' phenomena of 

 motion in the animal organism ' 

 (Liebig, ' Die organische Chemie, 

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



