ON METHODS OF DETERMINING THE DRYNESS OF STEAM. 399 



condensed in the barrel, till the temperature has risen to about 110° F. 

 The valve is shut, the movable pipe removed, the water stirred, and the 

 barrel again weighed and its temperature taken. It is obvious that the 

 proceeding is a very rough one. Losses of heat by radiation, &c., tend to 

 make the observed total heat too small, and therefore the moisture in the 

 steam too large. On the other hand, evaporation from the barrel tends 

 to make an error of the opposite kind. It is known that in using this 

 method in a rough way negative results are sometimes obtained. 



Mr. P. W. Willans used this method also to determine the wetness 

 of the steam in his engine trials.' Mr. Willans used a very large con- 



FiG. 3. 



densing tank weighing full about 3 tons, and placed on the platform of 

 a weighing machine. The tank was first balanced so that the weighing 

 machine lever just rose. Then a standard hundredweight was placed on 

 the platform of the machine, and the poise adjusted so that the lever 

 again just rose. The hundredweight was then removed, the temperature 

 of the condenser was noted, and steam condensed in the tank till the 

 lever rose (making an electric signal). The steam at that moment was 



' ' Economy Trials of a Non-condensing Steam Engine,' by P. W. Willans, Proc. 

 Imt. Civil Engineers, vol. xciii. p. 23. 



