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PROCEEDINGS OF THE AMERICAN ACADEMY. 



due to the slight difference between the step and reversal methods which 

 still remains. It is thus probable that the material of these two rods is 

 not of very great importance. The curve for m = 240 was also taken, 

 but was very nearly coincident with that for m = 200. 



When this rod, which we will call Rod No. I, was tested for conse- 

 quent poles, there was also selected another one of the same diameter 



10 



Figure 12. 



15 



80 



Effect of consequent poles in an iron rod. The magnetization curves shown 

 were taken under apparently the same conditions. 



from the same lot of iron. Both were 20 feet long, and pieces of 1 

 foot and 4 feet were cut off from the ends. Rod No. II was magnetized 

 at m = 240, and gave the higher curve marked by the crosses. The 

 pieces of 4 feet length had been mixed up so that it was impossible to 

 say which belonged to Rod No. I and which to the other one. Test 

 pieces of m = 60 were now prepared from both of these pieces, all of 

 these rods of diameter 1.905 cms. being wound with 50 secondary turns 



