90 



2. On the Computation of the Specific Heat of Liquid Water 



at various Temperatures, from the Experiments of 

 M. Regnault. By W. J. Macquorn Rankine. 



The experiments of M. Regnault having been made by intro- 

 ducing water at a high temperature from a boiler into a calorimeter, 

 containing water at a low temperature, and power exercised by 

 the steam in the boiler in expelling the water was converted into 

 heat by fluid friction, thus producing a rise of temperature in the 

 calorimeter, for which allowance ought to be made in calculating 

 the specific heat of liquid water from each experiment. Mr Joule's 

 determination of the dynamical value of the specific heat of liquid 

 water at low temperatures aiFords the means of calculating the cor- 

 rection required in each case. 



The author of this paper having thus corrected several of the re- 

 sults computed by M. Regnault, shews that they agree nearly with 

 this empirical formula : — 



|^ = 1.<.(T-T.) = 



Where K is the specific heat of liquid water at the temperature 

 T of an air thermometer, K^ its specific heat at T^, the temperature 

 of its maximum density (which is 4*1° centigrade, or 39-4° Fahr.) 

 and a, a constant coefficient, whose values are — 



For the centigrade scale, . . 0-000001 



For Fahrenheit's scale, . . 0-000000309 



The paper is illustrated by three tables : the first shewing the 

 correction of M. Regnault's results ; the second exhibiting a compa- 

 rison between the experiments and the formula, and the third giving 

 the results of the formula for every tenth degree of the centigrade 

 scale, from 0° to 260°. 



3. On the Quantities of Mechanical Energy contained in a 



Fluid Mass, in different states, as to Temperature 

 and Density. By Professor William Thomson. 



Let p be the pressui-e of a fluid mass when its volume and tem- 

 perature are v and t respectively, and let Mc^ v + N rf « be the 



