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PROCEEDINGS OF THE AMERICAN ACADEMY. 



1.9 centimeters in diameter inside. OCL represents the flux through 

 the central cross section of the shell when the current was running, and 

 the lower curve shows the residual flux upon a relatively larger scale. 

 This residual flux is reversed for solenoid fields less than about 200 

 gausses. 



Figure 7. This diagram shows magnetic bias in a short rod of cold-drawn 

 mild steel. This resisted the ordinary processes for demagnetizing the iron. 



The three pieces of steel to which the curves of Figures 3, 4, and 5 

 belong were all freshly annealed just before they were- magnetized, and 

 the same precaution was taken in the case of almost every other speci- 

 men mentioned in this paper. The most careful reannealing does not 

 generally bring a stout piece of iron which has been exposed to a 

 strong field exactly back to its original magnetic state, though the 

 differences are often so small as only to be discoverable when the speci- 

 men is tested for anomalous magnetization. Figure 6 shows such a 

 test made upon a soft piece of Bessemer steel freshly annealed before 

 the observations recorded in each curve. The residual moments were 

 themselves very small and the differences were in absolute value very 

 small indeed but are evidently real. 



Figures 7 and 8 show the results of experiments made upon two 

 pieces 12 and 8 centimeters long, respectively, cut from a rod of cold- 

 rolled shafting about 3 centimeters in diameter. Each piece was ex- 

 posed to a long series of magnetic fields alternating in direction and 

 gradually decreasing in intensity, with the hope that this process 

 would remove any magnetization that the rod might have acquired in 

 the making, but both pieces show a decided bias which was too strong 

 to yield to such treatment. In Figure 7, OPQ is the residual mag- 

 netism after currents which have caused positive moments have been 



