26 Prof. A. Schuster and Mr. W. Gannon. [Nov. 22, 



have safely done if the length of time the current passed had to be 

 measured with great accuracy. 



The Results. 



We divide our experiments into three series, but only attach any 

 value to the third, as during the first two sets the thermometer was 

 falling in the last period. We had hoped at first to be able to apply 

 a small correction to eliminate the error which is due to the fact that 

 a falling thermometer will read too high, and we made a large number 

 of experiments to determine the correction. We arrived, however, 

 at the result that the indications of a falling thermometer are BO 

 irregular that no correction is possible. Consequently in our third 

 series the thermometer was rising during the whole course of each 

 experiment. 



We think it worth while to put on record an impression that the 

 behaviour of our Baudin thermometer has altered since we first 

 received it from the maker. As soon as it came some preliminary 

 experiments were made to see if we could work with the thermo- 

 meter while it was falling, and the observations seemed to show that 

 the fall was sufficiently uniform. Our first three experiments gave 

 results which were very consistent, and a minute after the current was 

 broken the temperature seemed to fall already in a perfectly regular 

 manner. But as we continued our work, the behaviour of the instru- 

 ment seemed to deteriorate. Thus, in our experiment on March 8, 

 the temperature had hardly fallen three minutes after the current 

 had stopped. It is possible that this is due to accidental circum- 

 stances, for it is well known that different places of the bore of a 

 capillary tube behave very differently. We wish, therefore, to ex- 

 press no opinion at present as to the probability of an actual -change 

 in the thermometer, but only to draw the attention of other experi- 

 menters to this point, which seems worth keeping in mind. 



Our final value is 



J = 4-1804 Joules on the mercury scale of hard French glass, 

 4*1905 on the nitrogen scale, 

 41917 on the hydrogen scale, 



at a temperature of 19'l. 



This result depends on the assumption that the electrochemical 

 equivalent of silver is 0-001118, and that our standard Clark cell had 

 an electromotive force of 



1-4340(1 **- 15) volts, 

 where 



a = G'000814 + 0-000007 (f 15), 



