548 Mr. Seibei Konno on the Variation of 



cd, ef, a'b\ and ah were taken ; and again the same obser- 

 vations were repeated by reversing the poles o£ the 

 galvanometer leads pp, by turning the glass tube H, the 

 disturbing effect of the thermoelectric current in the circuit 

 leading to the galvanometer being thus eliminated. The 

 difference between each pair of these readings corresponds 

 to 28 in the above formula. The heat generated in the 

 cavity F per unit of time was then measured by observing 

 the current passing through the heatino-coil and its terminal 

 volt. Finally, the temperature of the specimen and its 

 gradient were re-determined for confirmation. Next, the 

 current in the heating-coil was broken, and a current passed 

 through the furnace. When the temperature of the furnace 

 was raised by a certain amount, another current was passed 

 through the heating-coil F ; after the temperatures had 

 become stationary, the observations were repeated as above. 

 In this way the observations at gradually increasing tem- 

 peratures were made step by step. It was found that the 

 interval required for the approximate stationary state 

 gradually decreases with the rise of temperature, the 

 smallest, however, being 30 minutes. 



§ 4. Results of Experiments. 



In order to see how much of the heat generated in the 

 coil is lost before entering the iron piece D, the specimen C 

 was removed and the pieces B and D were brought in direct 

 contact, and the temperature-gradients in the two junctions 

 cd and a'b' were observed. The gradient in the second 

 junction was about 30 per cent, less than that of the first 

 junction. With the specimen in its proper position, this 

 difference was not in any case greater than 40 per cent.; 

 hence the portion of the loss due to the lateral conduction 

 through the specimen is of the order of magnitude of 

 10 per cent. It is, however, a merit of the present method 

 that a fairly correct value for the conductivity is always 

 obtained. In order to show this, the absolute determination 

 of the thermal conductivity of a carbon steel containing 

 0*35 per cent, of carbon was measured. As the results of 

 the experiment we obtained the following values : 095 

 at 128° C, 0-088 at 305° C, 0'072 at 473° C. These values 

 agree very satisfactorily with those obtained by Prof. Honda 

 and Mr. Shimizu*. In the actual case the determination of 

 the conductivity was made relative to the conductivity at 

 room temperature. 



* Sci.Kep.vi. p. 219(1917). 



