122 THOMSON'S COURAGE IN EXPRESSING DOUBTS. 



however, we meet with innumerable other difficulties — in- 

 superable without further experimental investigation and 

 an entire reconstruction of the theory of heat from its 

 foundation. It is indeed to experiment we must look, 

 either for a verification of Carnot's axiom and an explana- 

 tion of the difficulty we have been considering, or for an 

 entirely new basis of the theory of heat." 



This note contains the last doubt or difficulty ever 

 expressed by Sir William Thomson as to the full accept- 

 ance of all Joule's views, and, not only so, these quotations 

 from Sir William Thomson's papers on Carnot's theory, 

 published in 1848 and 1849, contain the only expressions of 

 doubt ever published as to the sufficiency and conclusive- 

 ness of Joule's demonstration of the reciprocal convertibility 

 of heat and mechanical effect, or as to the conclusions 

 which Joule himself had drawn from them as to the 

 mechanical character of heat. The propriety of introducing 

 them in this memoir thus becomes evident, and it is also 

 evident that any apology to the author of these doubts is 

 not only unnecessary but would be out of place. 



The expression of these doubts, before any other 

 physicist had made any admission as to the importance or 

 taken any public notice whatever of Joule's work, shows 

 that Sir William Thomson, besides having the courage 

 beyond all others to publicly announce and acknowledge 

 the importance of discoveries, the truth of which, how- 

 ever adverse to the views he then held, he could not deny,, 

 alone had sufficient confidence in his own judgment,, 

 knowledge, and scientific acumen to maintain the truth of 

 what his judgment convinced him was true in the previous 

 theory, and while admitting the force of the new theory, 

 to withhold his full acceptance, until by clearly seeing 



