8 Peirce — Magnetic Properties at High Excitations. 



From 77=1100 up to 77=2450, the observed values of I 

 differ on the average from their mean by about one-sixth of 

 one per cent only. 



For high excitations, corresponding values of 77 and B may 

 be obtained from the equation 7?= 77+21840. 



Table IV shows the results of some determinations of the 

 maximum value of /made upon an isthmus piece of the iron 

 P after it had been subjected to an annealing process lasting 

 about 48 hours and was therefore extremely soft. 



Table IV. — Specially Annealed Isthmus Piece of Norway Iron 



(Cross section of isthmus 0'2050 square centimeters ; mean area of inner 

 test coil 2230 square centimeters ; mean area of outer test coil 0*5025 

 square centimeters.) 



Exciting Current 



H 



B 



I 



l'OO 



5920 



28580 



1799 



4-07 



12370 



34900 



1794 



5-58 



13720 



36210 



1790 



9-90 



16000 



38530 



1793 



23-00 



18130 



40780 



1802 



31-00 



18810 



41400 



1797 



For a current of about 55 amperes a value 7?=42200 was 

 reached but the current fell so rapidly that H could not be 

 accurately determined. In this case the excitation was upwards 

 of 160,000 ampere-turns. 



It is interesting to compare this remarkable value for the 

 maximum intensity of magnetization with that obtained for a 

 specimen of the iron R, after it had been thoroughly annealed. 



Table V. — Annealed Norway Iron (R) in Massive Yoke. 



(Free length about 80 millimeters.) 



H B I 



800 22770 1748 



900 22880 1749 



1000 23000 1750 



1500 23500 1751 



1800 23810 1751 



2000 24010 1751 



2350 24360 1751 



The Jefferson Laboratory, Cambridge, Mass. 



