Till: TllKKM'ihYXAMICAL PROPERTIES OF SUPERHEATED STEAM. 



13 



Barometric height. Time. 



30-164 T58 



30-160 2-53 



30-153 3-51 



Temperature of air. 

 62-0 

 62-5 

 62-5 



TABLE II. 



In the lower of these tables is given the corrections and the corrected values of the 

 mean temperatures and pressures drawn from the fourth and fifth columns in the first 

 table. 



An experiment usually lasts from 6 to 8 hours, during which time three to 

 six mean values of T 2 for different values of p a will be found for any initial pressure 

 and temperature in the reservoir. 



SECTION VIII. The Correction of the Pressure Gauges. 



The Bourdon pressure gauges used during the experiments were corrected by 

 means of a Bailey pressure gauge testing machine. In this machine the gauge is 

 subjected to hydraulic pressure, obtained by placing as many weights as required 

 ujxm a ram. The machine itself was subjected to examination by checking all the 

 weights used, and also the sectional area of the ram ; in this way the pressure per 

 square inch produced by placing any weight upon the ram could be directly calculated. 

 A further test was also made for small loads by the use of a mercury column to 

 balance the pressure produced by the dead load on the ram. 



The pressure gauges when tested showed the usual discrepancies of such gauges, 

 but in tests made at various times during the research, the amount of the corrections 

 was very closely determined. Especially was this the case with the pressure gauge 

 used above the orifice, as it was by this gauge that the thermometers were corrected, 

 and it is improbable that the error in the gauge when finally corrected could exceed 

 O'l Ib. per square inch in any part of the scale. 



