Specific Heat of Water. 



305 



correct data, especially as they agree with his values in the 

 twenty-seven other experiments. 



I have applied this test to the thirteen experiments, and 

 find that it is satisfied in all in the manner illustrated by the 

 following- six examples. The last column but one contains the 

 values of x as found approximately. 



No. of 



experiment. 



T. 



U 



t. 



Specific Heat. 



Kegnault. 



Approximate. 



Velten. 



35. 

 36. 

 37. 

 38. 

 39. 

 40. 



> 



183 



► to 



190 



) 



13 

 to 

 13-6 



( 

 28 

 to - 

 29 



101430 

 1-01499 

 1-01756 

 1-01487 

 101621 

 1-01528 



1017 

 1-019 

 1-019 

 1019 

 1-020 

 1-020 



•9748 

 •9749 

 •9798 

 •9804 

 •9757 

 •9799 



It is thus seen that Regnaulfs experiments are still reliable 

 and remain the most valuable which we possess on the subject 

 of the variation of the specific heat of water with temperature. 

 Yelten considers that his values calculated from Regnault's 

 data confirm a formula which he has given for the specific 

 heat of water deduced from experiments below 100°, and 

 which makes the specific heat of water above 100° less than 

 unity ; but we see from the above that his formula is quite 

 out of harmony with Regnault's experiments. 



Rankine (* Transactions of the Royal Society of Edinburgh,' 

 xx.) has pointed out a correction which is required in 

 Regnault's equation to allow for the kinetic energy of 

 the hot water projected into the calorimeter by the high- 

 pressure steam ; but it is perhaps hardly necessary to apply 

 it till greater precision is attained in the calorimetric 

 measurements. 



It would not have been worth while treating the matter at 

 such length were it not for the large amount of experimental 

 work that has already been spent on the subject and the 

 importance of showing that the experiments of so skilled a 

 physicist are not lost as they appeared to be, and of removing 

 an unmerited reproach from so respected a name. 



Melbourne, 



May 25, 1888. 



Phil. Mag. S. 5. Vol. 26. No. 160. Sept. 1888. 



X 



