(534 Mr. H. E. Schmitz on the 



points on this circuit separated by 3019 ohms gave a prac- 

 tically constant electromotive force of about '03 volt, serving, 

 in a manner which will presently appear, to standardize the 

 apparatus for measurement of thermoelectromotive forces. 



The thermometers on which the main temperature measure- 

 ments depend were two, graduated respectively from —15° C. 

 to + 60° C, and from + 50° C. to + 120° C, the length of the 

 degree being about 5 mm.; they were manufactured from 

 Jena glass by F. O. R. Goetze. In what follows these 

 thermometers are called respectively G and G x . Com- 

 parisons with a standard mercurial thermometer gave the 

 following approximate results : — 



At 20° G reads *06° above the gas-thermometer, 

 „ 60° G x „ -06° „ 



OAO '01° 



The chief temperatures of observation were chosen with 

 the view of minimizing the importance of any error in the 

 correction for the emergent column ; this correction had the 

 following mean values : — 



+ '02° at 



20° 



(Go), 



zero at 



60° 



(Gi), 



+ •20° at 



80° 



(Gi). 



After the conclusion of the experiments the thermometers 

 were examined at the Reichsanstalt, with the following- 

 results : — 



At 20° G reads 'll above the gas-thermometer, 

 „ 60° G, „ '08° „ „ „ 



80° -03° 



The differences here indicated are, very nearly, the true 

 differences between the scale of Jena glass and the scale of 

 the gas-thermometer, the inference being that the actual 

 reading of the thermometer is, very nearly, the true tem- 

 perature on the scale of Jena glass. In what follows the 

 thermometers are taken as correct, and the temperature- 

 scale employed is therefore that of Jena glass. 



§ 3. Method. 



The observations were directed to determine (1) the electro- 

 motive force of each pair of metals between 0° and 20°, 

 between 0° and 60°, and between 0°and 80°; (2) the electro- 

 motive force of the circuit of three metals, the temperatures 



