io Reynolds, Dryness of Saturated Steam, 



than T 2 , equation (6) gives Si in terms of K which is a 

 function of T 2 and T 2 ', which has not been determined. 



If it were possible to determine the exact value of T 2 ' 

 at which S 2 — 1 = 0, then 



S x (H 1 —h 1 )+h l = H 2 . 



But, here again, this is practically impossible, since 

 the only indication that S 2 — 1=0 is that T 2 ' is 

 greater than T 2 as given by Regnault's tables for 

 steam at P 2 ', and, for any such excess as can be 

 observed, the value of K (T 2 ; — T 2 ) is considerable, since, 

 at the point of saturation, K is apparently infinite, so 

 that neither of these determinations are practical. 



With a view to getting over these difficulties, the 

 course that has apparently been adopted is to obtain a 

 condition such that the temperature (T 2 ') after wire- 

 drawing is from io° to 20° F. higher than the saturation 

 temperature (T 2 ), and then to assume that K is equivalent 

 to the specific heat at constant pressure of steam gas as 

 determined by Regnault, or that 



K = jj2 xo*48, 



an assumption which constitutes the error in reduction 

 to which I have referred. 



The possibility of obtaining an accurate estimate. 



This depends on obtaining a certain condition in the 

 experiment, and reducing by a formula proved by Rankine 

 (Trans. Roy. Soc. Edinb., 1849, I 855). 



Rankine's formula is that the total heat to convert 

 water from a liquid state at any particular temperature, 

 say 32 0 , to steam gas at any temperature (T 2 ')> the 

 operation being completed under constant pressure, is ex- 

 pressed by 



H=Ci+« (17-33°), 



