BABBITT. — THE VON WALTENHOFEN PHENOMENON. 



249 



The temperature of the room at the end was 18.3° C 



The temperature of the room dropped gradually during the course 



of the work. However, as three hours were required for the completion 



of one such set of data, the 



change was very gradual, and 



owing to the care taken to 



keep windows, doors, and 



heating appliances un- 

 changed during that period 



and for some time before it, 



the rate of the drop was 



practically constant. This 



would prevent anything more 250 



than a gradual change in the 



iron or the galvanometer and 



could not be regarded as 



the cause for any sudden 



variation in the curve. 



The galvanometer, as us- 

 ual, showed that it could be 



relied on to give an accuracy of 0.1 of a per cent. The difference 



between a throw for a reversal, 16.77, calculated from breaking the 



primary circuit of the testing solenoid, and the observed throw for a 



30 



100 



REVERSALS 



Figure 10. Set I: B 3000: first mag- 

 netization; O indicates 1-step reversal. 



Figure 11. Set I: B 3000: third magnetization; all 3-step reversals. 



reversal, 16.78, shows that there is in this case practically no correction 

 for leakage. In fact the leakage seemed to occur only when most of the 

 secondary of the toroid was in use. If one were not willing to make 



