2 Grindley, Thermodynamics of Superheated Steam. 



the same range of pressure and temperature as that 

 covered in the actual experiments. 



It must, however, be understood that this table is to be 

 considered as a useful auxiliary to the usual tables of the 

 properties of saturated steam compiled from Regnault's 

 experimental data, as the figures in it are deduced by a 

 previous knowledge of the properties of saturated steam, 

 and are therefore subject to the same errors, though it is 

 not likely these will be very appreciable. 



In the following section I propose to shew the kind of 

 results to which we are led when we rigidly adhere to the 

 data given by Regnault and the laws deduced by him for 

 the saturated condition of steam. 



II. On the specific heat at constant pressure (K^) z« 

 Stiperheatcd Steam. 



The most popular method, up to the present, of 

 deducing the value of Kp for superheated steam is that of 

 wiredrawing by free expansion saturated steam in a 

 known initial condition, the total heat of formation of the 

 steam in that condition being assumed to be that given by 

 steam tables founded on Regnault's experiments. 



What is really required, however, for the purpose of 

 determining the value of K,. by this method, is a know- 

 ledge, not of the actual total heat of the steam in any dry 

 saturated condition, but of the rate of variation of this 



quantity with temperature. 



The law of variation given by Regnault, for the total 



heat of formation of dry saturated steam, is the linear one 



^= 10917 + -3o5(«- 32) B.T.U's. 



the variation being assumed to be linear and to have the 



constant value '305. Now, from the data obtained b}' the 



author in his paper already mentioned, determinations of 



