Some Experiments on the Latent Heat of Steam. 53 



and the excess above this temperature of the measuring 

 junction was determined by direct deflection of a suitable 

 low-resistance galvanometer. As, however, this con- 

 siderably increased the work of an experiment, a second 

 observer not being available, it was omitted in the later 

 experiments, since it was found that after half an hour's 

 heating the lower part of the ebonite tube always reached 



100°. 



As the calorimeter rose during the " middle period " 

 about one degree per minute, the lag of the thermometer 

 was found to be considerable, and consequently was deter- 

 mined approximately for this rate of rise, the resultant 

 correction being an addition of about *i° to each of the 

 readings during the passing in of the steam. 



The experiments were carried out almost exactly as 

 described in the preliminary paper, except that an auto- 

 matic signalling arrangement gave a warning, and indicated 

 the time for the thermometer readings to be made by the 

 observer at the telescope. 



After one or two preliminary experiments to test the 

 working of the apparatus, a series of eight consecutive 

 determinations was made with superheated steam, the final 

 corrected results of which are given below. One experi- 

 ment is omitted on account of a slight uncertainty in one 

 of the corrections. 



(1) 640-2 (5) 643-4 



(2) 638-7 (6) 643-4 



(3) 639*5 (7) 641-6 



(4) 639-9 



Mean = 640-9 



Three experiments were also made, using steam direct 

 from the boiler without superheating ; the mean of them 

 was 639-0, a little lower than the above result, but as the 

 probability in this case that the steam enters the calori- 

 meter in a dry state, is not so great, I prefer to omit 

 them from the general result. The mean of the above 



