224 



IIIi: AMERICAS A< Al'K.MY. 



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

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

 Dot of very great importance. The carve form = 240 was also taken, 

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



When this rod, which we will call Hud No. I, was tested for© 

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



10 



Figure 1. 



15 



20 



Effect o quent poles in an iron rod. The magnetization curves - 



were taken under apparently the same conditions. 



from the same lot of iron. Both were 20 feet long, ami piece- of 1 

 foot and I 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 rod- of diameter 1.905 cms. being wound with "><i secondary turns 



