﻿26 Prof. E. Edlund on the Electromotive Force 



with cold water. In order that the water might be warmed very 

 slowly by the air in the room, the glass beaker was coated with 

 a layer of cotton- wool and covered with a pasteboard disk, through 

 a hole in which the test-tube was inserted. In this test-tube was 

 placed a delicate thermometer, and the space at the top between 

 the wires and the thermometer stopped with cotton-wool. Thus 

 the temperature of the test-tube was kept constant long enough for 

 the place of soldering to acquire the temperature which the ther- 

 mometer indicated. The free ends of the wires were connected 

 with the conducting-wires of the magnetometer, which were of 

 copper. The connexion between the two different metals was 

 surrounded by cotton-wool, after the bulb of a delicate thermo- 

 meter had been adjusted as near the place of contact as possible. 

 The deflections of the magnetometer, which were read off in the 

 usual manner with a telescope and scale, were proportional to the 

 intensity of the current. The conducting-power in the circuit 

 for thermoelectricity was measured by means of a magneto- 

 inductor, the coil of which was inserted in the circuit. The 

 deflections which were obtained by the induction-currents caused 

 by the inductor gave thus a measure for the conducting-power. 

 In what follows I will merely give the mean numbers obtained. 

 Experiment 13. — Bismuth-copper. 



The deflection = 205*5. The difference of temperature at the 

 two places of contact = 12°*8. With the magneto-inductor a 

 deflection of 174 divisions was obtained. Hence this number 

 represents the conductivity in the path of the thermoelectric 

 current. 



Experiment 14. — Argentan-copper. 



Deflection =61*8. Difference of temperature = 11°*9. 



Conducting-power = 224*0. 

 Experiment 15.— Platinum-copper. 



Deflection = 22*0. Difference of temperature = 11 0, 8. 



Conducting-power = 226-5. 

 Experiment 16. — Zinc-copper. 



Deflection = 2*5. Difference of temperature = 12 0, 1, 



Conducting-power = 230*5. 

 Experiment 17.- — Silver-copper. 



Deflection = 2*0. Difference of temperature = 13°* 7. 



Conducting-power = 232*0, 

 Experiment 18. — Copper-iron. 



Deflection = 73*0. Difference of temperature = 12 0, 8, 



Conducting-power = 228*8, 

 In these metallic combinations the thermoelectric current went 

 at the warmer place of contact from the first-named metal to the 

 succeeding one. 



