100 MR. J. P. JOULE ON EXPERIMEJSTS 



with the worm, the operator was enabled in all cases to 

 operate under similar circumstances as to the relative 

 pressures of tlie steam and atmosphere. 



In my own experiments, a vulcanized india-rubber tube, 

 eight inches long, was attached to the nozzle of a short 

 pipe (furnished with a stop-cock), connected with the top 

 of an upright boiler. To the end of the india-rubber tube 

 a brass nozzle was attached. The stop-cock was left con- 

 stantly open. In making an experiment the brass nozzle 

 through which the steam was blowing was suddenly 

 plunged into a can of water and then, after two or three 

 minutes, suddenly removed again. The weight gained by 

 the can indicated the quantity of water condensed, which, 

 with the observations of temperature before and after the 

 experiment, afforded the means of computing the total 

 heat of the steam. 



The requisite corrections were readily made and not of 

 large amount. They arose from the heat lost by the 

 steam by conduction in passing from the boiler to the can, 

 the thermal effects of the atmosphere on the can itself, 

 and the evaporation of the water from the can which took 

 place before the weighing was accomplished. The data 

 for these were derived from observations made after each 

 experiment. The following table comprises the results I 

 obtained : 



