410 



REPORT — 1894. 



chambers of the insti'umenfc. Let t^' be the temperature in the first 

 chamber, t^ the temperature in the second chamber after wire-drawing. 

 Apart from any loss by i-adiation, and assuming that the kinetic energy 

 due to passage through the orifice is reconverted by friction into heat, the 

 difference of temperature in the two chambers can be calculated. Let^j, 

 be the pressure in the first chamber, and t^ the corresponding temperature 

 of saturated steam ; 2)2 ^^^ pressure in the second chamber, and t.2 the 

 corresponding temperature. Since the total heat per pound is the same in 

 both chambei's, 



1082 + 0-305<i + 0-48(<i'-«i) = 10S2 + 0-305<2 + 0-48(«2'-«2) 

 i!/— i!2'=0-3646(<i— iJa). 



In the following experiment the pressure in the second chamber was 

 slightly greater than atmospheric pressure, and the corresponding tem- 

 perature was 215°. Putting in this value 



«/-«,'=0-3646<,-78-4. 



Test of the Barrus Wire-drawiiig Calorimeter at the Central Technical 

 College with Superheated Steam. — The steam was taken from a Babcock 

 Wilcox boiler, and the engine was running. Steam valve opened at 

 2*^ 49™ and gas jets of superheater lighted at 3'" 1™. Barometer 30-02 

 =14"75 lb. per sq. in. Pressures taken by a Schaffer and Budenberg gauge. 



The mean superheat in the first chamber was 24°. That in the 

 second chamber 80°'l. There could be no doubt therefore as to the quality 

 of the steam. The observed difference of temperature t/ — ^2' '^^^ remark- 

 ably constant, and the differences from the calculated values are not great. 

 The mean difierence of the observed and calculated values of ti'—t2'is 

 only 0"67. Necessarily the common pressure gauge readings are only 



