MAYER 273 



Mayer injured his legs badly, and only gradually recovered in 

 Wildbad. This was by no means the end of his troubles. 

 They even became worse, in a manner which did great dis- 

 credit both to the representatives of science as to those of 

 medicine. But we will proceed with this story after first 

 discussing his work. 



When we read to-day Robert Mayer's three main publica- 

 tions^ we can only once more be astonished at the richness of 

 their contents; they bring in the main already everything 

 fundamental to the energy principle, and we may also be sur- 

 prised to find therein very much that, even to-day, is still 

 fairly generally ascribed more to his successors than to 

 himself.^ The first paper (1842) puts the discovery in a 

 very condensed form, without any argument based on de- 

 finite facts; ^ however, the mode of calculating he tmechanical 



1 'Bemerkungen uber die Krafte der unbelebten Natur,' 1842; 

 'Die organische Bewegung in Zusammenhang mit dem StoflFwechsel,* 

 1845; 'Beitrage zur Dynamik des Himmels,' 1848. A translation of these 

 will be found in The Correlation and Conservation of Forces, a series of 

 expositions by Grove, Helmholtz, Mayer, Faraday, Liebig, and Carpen- 

 ter, with introduction and notes by Youmans; New York, 1865. 



2 Thus for example, the idea which has become more and more im- 

 portant in regard to the temperatures of the fixed stars, that shrinkage 

 under the influence of force must result in the production of fresh quan- 

 tities of heat, is already clearly stated in the paper of 1845 (second part of 

 section 3). Later (in the 1848 paper) Mayer put forward the fall of 

 meteoric masses into the sun as the chief means of maintenance of its 

 temperature, but without at all cancelling the other suggestion. 



3 The turns of expression used there and elsewhere by Mayer, such 

 as 'ex nihilo nil fit,' 'nil fit ad nihilum, "causa aequateffectum' (nothing 

 is made out of nothing, nothing is annihilated, the cause is equal to the 

 effect) are not to be regarded as proofs or preliminary axioms (as has often 

 been stated by way of adverse criticism) but as short expressions of our 

 knowledge, thrown off by way of humorous explanation. Mayer was 

 also fond at other times of these turns of speech, and his humour was 

 well known. These phrases may be regarded - following Mach - 

 as the sign 'of a mighty, instinctive, and still unsatisfied need for a sub- 

 stantial view of what we to-day call energy,' in which mode of expression 

 'Mayer in no way behaved differently from Galileo, Black, Faraday, and 

 other great men of science.' The view of energy as a substance has 

 actually, quite recently, turned out to be perfectly tenable (see the re- 

 marks concerning Hasenohrl, at the close of the book). The humour of 

 great minds is always of significance; it is always understood only long 

 afterwards. 



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