ACCEPTS JOULE'S EQUIVALENT. 1 27 



greater than the true value. The difference between the 

 result I have just stated and those at which he arrived do 

 not seem greater than those causes are capable of producing 

 when combined with the uncertainty of experiments, like 

 those of Mr. Joule, on extremely small variations of tem- 

 perature." 



That these criticisms of Rankine's should, when he first 

 saw them, have been painful to Joule, there is no wonder ; 

 at the same time he must (knowing as he did the in- 

 sufficiency of Rankine's data ; having himself previously 

 followed the same determination by Laplace's theory), have 

 anticipated the result. This followed the same year. 

 Rankine's paper was read, February, 1850; on December 

 2nd, another paper of Rankine's was read, in which he ex- 

 plains that since his reflections on the accuracy of Joule's 

 experiment, he has seen the detailed account of Mr. Joule's 

 last experiments in the PJiilosophical Transactions for 1850, 

 which, he continues, "have convinced me that the uncer- 

 tainty arising from the smallness of the elevations of tem- 

 perature is removed and that the necessary 



conclusion is, that the dynamical value assigned by Mr. 

 Joule to the specific heat of liquid water, viz., 772 feet per 

 degree of Fahrenheit, does not err by more than two or at 

 most three feet, and that, therefore, the discrepancy 

 originates chiefly in the experiments of De la Roche and 

 Berard." 



" I therefore take the earliest opportunity of correcting 

 such of my calculations as require it so as to correspond 

 with Mr. Joule's equivalent." 



There is no doubt that whatever was lost in the generality 

 of Rankine's mechanical theory of heat from its hypothetical 

 foundation, that the definition and suggestiveness arising 



