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PROCEEDINGS OF THE AMERICAN ACADEMY. 



to a high superheat. The amount of energy necessary for the super- 

 heating was then found by a subtraction. It is, therefore, liable to a 

 percentage error much greater than that in either of the observed 

 components. Knoblauch's method is obviously preferable to Thomas' 

 in this respect. 



His experimental arrangements also seem superior to Thomas'. In 

 his separate calorimeter there were only small temperature differences 

 between the inlet and outlet pipes ; in Thomas' combination calori- 

 meter there were very large differences. In Knoblauch's case the heat 

 losses through these pipes were determined ; in Thomas' case they 



Figure 1. Knoblauch's Cp. diagram. 



were ignored. Furthermore, although both calorimeters were very 

 carefully lagged, Knoblauch determined his radiation losses in each 

 experiment, while Thomas, in the final form of his apparatus, relied on 

 eliminating them, a difficult thing to be sure of. Finally, Knoblauch's 

 thermometry is apparently more refined than Thomas'. It is there- 

 fore probable that wherever the two sets of results disagree, Knob- 

 lauch's are to be preferred. 



As a matter of fact, the two sets of results agree fairly well in the 

 region of moderate superheats, as will be seen in Figures 1 and 2, but 

 disagree fundamentally in exactly that part of the diagram which will 

 be most used in what follows, namely, the region of moderate pressures 

 and very low superheats (the lower left-hand corner of Figure 1). The 



