304 



B. 0. Peirce — Thermo-electric 







Table I. 









Electromotive 



Forces. 



Temperatures of the 



Mercury vs. 



Platinoid vs. 



Junctions. 



Manganine. 



Mercury. 



0° and 



10° 



66 



123 



0° and 



20° 



136 



246 



0° and 



30° 



209 



372 



0° and 



40° 



283 



500 



0° and 



50° 



359 



631 



0° and 



6U° 



43S 



766 



0° and 



70° 



524 



906 



0° and 



80° 



613 



1048 



0° and 



90° 



704 



1190 



0° and 



100° 



797 



1331 



When the hard drawn manganine wire no. IS in a thermal 

 junction was for the first time raised to the temperature of 

 boiling water and then slowly cooled, the results of a series of 

 observations of electromotive force taken during the cooling 

 were sometimes rather irregular though they agreed in general 

 fairly well with the regular results (in complete agreement 

 with one another) obtained on a second, third, or subsequent 

 heating. The platinoid wire always gave regular results from 

 the first and these were repeated with a given specimen as 

 often as the junctions were brought to the same temperatures. 

 The annealed manganine wire showed no irregularities on first 

 being heated. The results of a large number of completely 

 accordant observations with thermo elements made of copper 

 and either platinoid wire no. 19 or manganine wire no. 18 are 

 given in the next table. 







Table II. 









Electromotive Forces. 



Temperatures of the 



Copper vs. 



Platinoid vs. 



Junctions. 



Manganine. 



Copper. 



0° and 



10° 



4-3 



189 



0° and 



20° 



9-2 



379 



0° and 



30° 



14-1 



572 



0° and 



40° 



19-6 



769 



0° and 



50° 



25-7 



971 



0° and 



60° 



32-6 



1179 



0° and 



70° 



40-2 



1391 



0° and 



80° 



48-1 



1609 



0° and 



90° 



56-4 



1834 



0° and 100° 



64-9 



2063 



The thermo-electric effects at the junctions with their cop- 

 per terminals of resistance coils would evidently be far less 

 under given conditions if the coils were made of this specimen 



