Mr. W. J. M. Rankine on the Mechanical Action of Heat. 3 



This hypothesis, like all others, is neither demonstrably true 

 nor demonstrably false, but merely probable in proportion to the 

 extent of the class of facts with which its consequences agree. It 

 must however be remarked, that whether the hypothesis be pro- 

 bable or improbable, the theoretical and practical results arrived 

 at in the following paper respecting the mechanical action of heat 

 remain unaffected, being deduced from principles which have 

 been established by experiment and demonstration. 



The chief contents are as follows : — 



The Introduction explains the hjrpothesis. 



The First Section treats generally of the mutual conversion of 

 heat and expansive power ; 



The Second Section, of real and apparent specific heat, espe- 

 cially in the state of perfect gas ; 



The Third Section, of the latent and total heat of evaporation, 

 especially for water. 



The Fourth Section treats of the mechanical action of steam, 

 treated as a perfect gas, and the power of the steam-engine, and 

 contains practical formulse and tables. In a supplement to this 

 section, the results of these formulse and tables are compared 

 with the experiments of Mr. Wicksteed on the Cornish engine 

 at Old Ford ; and a graphic solution is given of the problem, to 

 determine the rate of expansion in a Cornish engine, so that the 

 sum of the annual cost of fuel, and the interest of capital, shall 

 be the least possible as compared with the work done. 



The Fifth Section treats of the ceconomy of heat in expansive 

 machines generally. 



A sixth section was read to the Royal Society of Edinburgh 

 in January 1853, and is published in their Transactions. 



Besides the numerical corrections already referred to, the only 

 alterations which this paper has received consist in the addition 

 of some notes, the cancelling of some statements and calcula- 

 tions which have been superseded by subsequent researches, and 

 a few slight improvements in the notation. 



Glasgow, November 1853. 



On the Mechanical Action of Heat, especially in Gases and 

 Vapours*. 

 Introduction. 

 Summary of the Principles of the Hypothesis of Molecular Vor- 

 tices, and its application to the Theory of Temperature, Elasti- 

 city, and real Specific Heat. 



The ensuing paper forms part of a series of researches respect- 

 ing the consequences of an hypothesis called that of Molecular 

 * Read to the Royal Society of Eilinhurgh, Febniaiy 4, IH^O. [With 



