120 PROCEEDINGS OF THE AMERICAN ACADEMY 



III.— CALORIMETRY. 

 (a) Specific Heat of Water. 



The first observers on the specific heat of water, such as De Luc, 

 completed the experiment with a view of testing the thermometer ; 

 and it is curious to note that both De Luc and Flaugergues found the 

 temperature of the mixture less than the mean of the two equal por- 

 tions of which it was composed, and hence the specific heat of cold 

 water higher than that of warm. 



The experiments of Flaugergues were apparently the best, and he 

 found as follows : * — 



3 parts of water at 0° and 1 part at 80° R. gave 19°.86 R. 

 2 parts of " " 2 parts " " 39°.81 R. 



1 part of " " 3 parts " " 59°.87 R. 



But it is not at all certain that any correction was made for the 

 specific heat of the vessel, or whether the loss by evaporation or 

 radiation was guarded against. 



The first experiments of any accuracy on this subject seem to have 

 been made by F. E. Newmann in 1831.f He finds that the specific 

 heat of water at the boiling point is 1.0127 times that at about 28° C. 

 (22° R.). 



The next observer seems to have been Regnault,J who, in 1840, 

 found the mean specific heat between 100° C. and 16° C. to be 

 1.00709 and 1.00890 times that at about 14°. 



But the principal experiments on the subject were published by 

 Regnault in 1850, § and these have been accepted to the present time. 

 It is unfortunate that these experiments were all made by mixing 

 water above 100° with water at ordinary temperatures, it being 

 assumed that water at ordinary temperatures changed little, if any. 

 An interpolation formula was then found to represent the results; 

 and it was assumed that the same formula held at ordinary tempera- 

 ture, or even as low as 0° C. It is true that Regnault experimented 

 on the subject at points around 4° C. by determining the specific heat 

 of lead in water at various temperatures ; but the results were not of 

 sufficient accuracy to warrant any conclusions except that the variation 

 was not great. 



* Gehler, Phys. Worterbuch, i. 641. 



t Pogg. Ann., xxiii. 40. \ Ibid., li. 72. 



§ Pogg. Ann., lxxix. 241 ; also, TCel. d. Exp., i. 729. 



