I 



by Electricity. 431 



The deflection in this case was similar in direction to that pro- 

 duced when the warm finger was placed upon the junction. 



The wires w lo' were moved back to their former position, and 

 the apparatus was suffered to cool ; by crossing the wires b b', 

 causing the former to dip into m and the latter into m', the vol- 

 taic current was reversed, its direction across the junction being 

 now from bismuth to antimony ; the same time of circulation 

 being allowed, on establishing the thermo-eircuit, as before, a 

 deflection of 



68° 



was observed. The deflection was the same as that produced 

 when a small glass containing a freezing mixture was placed 

 upon the junction. 



But Mr. Adie will probably urge, that it is not the cold deve- 

 loped at J, but the heat developed at some of the other points, 

 which caused the deflection here. I will not pause to discuss 

 the objection, but will proceed to an experiment which deprives 

 it of all force. 



Experiment No. 2. — AA' is a bar of antimony, BB' is a bar 

 of bismuth cast as in fig. 2, and in contact at the centre. 

 From the cell B a current was sent through the system, and 

 during its circulation the ends g g' were unconnected ; neither 

 heating nor cooling of these ends by the current was therefore 

 possible. The direction of the current across the junction was 

 first from antimony to bismuth. After a short pei'iod of circu- 

 lation the current was interrupted, and the ends of the wires 

 IV ic' were dipped into the mercury cups g g', which were also in 

 contact with A'B' ; the index was driven through an arc of 



40°. 

 The sense of the deflection in this case showed that the junction 

 had been heated. 



The current was reversed, its direction across the junction 

 being now from bismuth to antimony ; proceeding as before, the 

 deflection was 



30°. 



The sense of this deflection was the same as that produced when 

 the temperature of the junction was loweredhy a freezing mixture. 



I see no escape here from the conclusion that heat has been 

 absorbed ; for the ends y g', exposed as they are to the atmo- 

 sphere, must have its temperature, while the ends m m', on which 

 suspicion might reasonai^ly rest, the current having passed 

 through them, are wholly excluded from the thermo-eircuit. 

 The reader will observe that this is merely a modification of 

 Lenz's experiment with the metallic cross. 



But Mr. Adie has tried the cross, and it does not satisfy him; 



