40 



AKT. 6. K. HONDA AND S. SHTMIZU. 



netometer, when there was any, was completely eliminated by 

 altering the form of the lead wires. The demagnetization by 

 reversals, while the heating current was passing, showed no trace 

 of residual magnetism, which indicates that the magnetization due 

 to the heating current was insensibly small. When the tempera- 

 ture became constant, the magnetizations at gradually increasing 

 fields were measured. Another stronger current was next sent 

 through the heating coil, and the same processes were repeated as 

 before. In this way, we measured the magnetization in the stage 

 of ascending temperature, and then that in the descending stage. 

 During each set of observations, the temperature was fairly con- 

 stant, and even in very unfavorable cases, it did not exceed 2 

 degrees. The temperature was always noted both before and after 

 each experiment, and the mean was taken. When a series of 

 experiments was finished, the specimen was taken out of the 

 coil, and the compensation tested. Excepting in a few cases, 

 we found the compensation undisturbed ; when, however, the 

 disturbance was such as to require a correction, it was uniformly 

 distributed. 



In the present experiment, the strength of the heating cur- 

 rent and the temperature thereby caused were as follows : — 



The heating of nickel steels protected in the manner above 

 described showed only a trace of surface-oxidation, if the tempera- 

 ture did not exceed about 800°C. If, however, the temperature 

 was raised to 1200°C, the surfece-oxidation became considerable, so 

 that the heating of some specimens was stopped at about 800°C, 



