HALL. — THERMO-ELECTRIC HETEROGENEITY IN ALLOYS. 569 



gerraan-silver wires warm is fully justified. It is doubtful whether on 

 any day these parts were kept warmer than the top of the cooler of the 

 two pots. It is reasonable to believe that, if an approximately uniform 

 gradient of temperature had been maintained in these parts from one 

 pot to the other, the differential percentage would have been reduced 

 still further. 



The Absolute Values of the Electromotive Force of the Couples. 



In the following table, (2) indicates that the observations were made 

 on couples A 2 , B 2 , etc.; (3) indicates that they were made with A 3 , B 8 , 

 etc. The column Max. -^Min. gives the ratio of the highest mean 

 electromotive force shown by any couple to the lowest mean electro- 

 motive force shown by any couple on the day considered. Results 

 obtained before July 21 are omitted from this table because of some 

 uncertainty as to the reduction factor of the galvanometer previous to 

 this date. Results obtained after September are separated from those 

 obtained earlier, because in the experiments made after September the 

 policy of keeping the middle parts of the german-silver wires warm was 

 followed, whereas in earlier experiments practically the opposite policy 

 was maintained. 



2386 

 2385 



