DAVIS. 



CERTAIN THERMAL PROPERTIES OF STEAM. 



299 



only small changes in the // formula, C p being a factor, not of H itself, 

 but only of AH. And in the second part of the computation, the re- 

 dependence of C p on H is again insensitive to errors in the assumed 

 function, which this time is H. All this can be strikingly illustrated 

 as follows. It is easy to compute approximately by the method of 

 Section 3 of this paper a value of AH near 140° and one near 180° 

 using Thomas' values of C p instead of Knoblauch's. These, with 



t 200 



Figure 12. Values of Cp computed by Planck's method. The dots are 

 based on the original volume measurements of Knoblauch, Linde and Klebe; 

 the circles are based on Linde's characteristic equation. The lower curve is 

 Knoblauch's saturation line; the upper one is Thomas'. 



AH = at 100°, give a new second degree equation for H=f{t) based 

 wholly on Thomas' values. Finally this new H equation can be used 

 with Linde's characteristic equation to compute, by means of Planck's 

 equation, a set of values of C p at saturation which are exactly com- 

 parable with those in the second part of Table VI., except that Knob- 

 lauch's C p work is wholly replaced by Thomas'. If there is a circular 

 fallacy in the confirmation mentioned at the beginning of this para- 

 graph, the new results ought to confirm Thomas' C p values at satura- 

 tion just as definitely as the old ones did Knoblauch's. As a matter 

 of fact, this is not at all the case. The new results are compared with 

 the old in Figure 13, and agree strikingly in confirming Knoblauch's 

 saturation curve. In other words, no matter which set of C p values 



