564 PROFESSOR WILLIAM THOMSON’S ACCOUNT OF 
Appendix. 
(Read April 30, 1849.) 
41. In p. 30, some conclusions drawn by Carnot from his general reasoning 
were noticed; according to which it appears, that if the value of uw for any 
temperature is known, certain information may be derived with reference to the 
saturated vapour of any liquid whatever, and, with reference to any gaseous mass, 
without the necessity of experimenting upon the specific medium considered. 
Nothing in the whole range of Natural Philosophy is more remarkable than the 
establishment of general laws by such a process of reasoning. We have seen, 
however, that doubt may exist with reference to the truth of the axiom on 
which the entire theory is founded, and it therefore becomes more than a matter 
of mere curiosity to put the inferences deduced from it to the test of experience. 
The importance of doing so was clearly appreciated by Carnot; and, with such 
data as he had from the researches of various experimenters, he tried his con- 
clusions. Some very remarkable propositions which he derives from his Theory, 
coincide with Dutone and Petit’s subsequently-discovered experimental laws with 
reference to the heat developed by the compression of a gas; and the experimen- 
tal verification is therefore in this case (so far as its accuracy could be depended 
upon) decisive. In other respects, the data from experiment were insufficient, 
although, so far as they were available as tests, they were confirmatory of the 
theory. 
42. The recent researches of RecnauttT add immensely to the experimental 
data available for this object, by giving us the means of determining with consi- 
derable accuracy the values of 4 within a very wide range of temperature, and so 
affording a trustworthy standard for the comparison of isolated results at different 
temperatures, derived from observations in various branches of physical science. 
In the first section of this Appendix the Theory is tested, and shewn to 
be confirmed by the comparison of the values of » found above, with those 
obtained by Carnot and CLapeyron from the observations of various experi- 
menters on air, and the vapours of different liquids. In the second and third 
sections some striking confirmations of the theory arising from observations 
by Dutone, on the specific heat of gases, and from Mr JouLE’s experiments 
on the heat developed by the compression of air, are pointed out; and in con- 

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