THE MAXIMUM VALUE OF THE MAGNETIZATION 

 IN IRON. 



By B. Osgood Peirce. 

 Presented February, 12, 1913. Eeceived May 3, 1913. 



The first experiments on the magnetic behavior of soft iron under 

 high excitations were made, more than sixty years ago, upon com- 

 paratively short, stout rods, so that the results were affected by the 

 demagnetizing action of the ends of the specimen, but, even under 

 these circumstances, several different observers ^ were able to show 

 that if the magnetizing force to which a piece of iron is exposed be 

 made stronger and stronger, the intensity of the resulting magnetiza- 

 tion of the metal usually approaches a definite limit, and that this limit 

 is practically reached in fields of such strength as are frequently used 

 in the laboratory. 



The work of Stoletow and Rowland in the early seventies of the 

 last century, upon iron rings or toroids, made the true meanings of 

 H, B, and I in the iron clearer, and since that time many persons ^ 

 have attempted to determine the limiting value {I^), of /, as H is 

 made to increase indefinitely. I^ is now sometimes called the specific 

 magnetism of the material. 



From some of his early work, to which he applied a peculiar method 

 of extrapolation, Rowland inferred that in the case of soft iron, I^ 

 must be about 1390, whereas Fromme obtained the value 1510 in 



1 Joule, Phil. Mag., 2, 1839; Mueller, Pogg. Ann. 79, 1850; 82, 1851; 

 Koosen, Pogg. Ann. 85, 1852; Dub, Pogg. Ann. 90, 1853; G. Wiedemann, 

 Pogg. Ann. 100, 1851; 106, 1859; 117, 1862. 



2 Rowland, Phil. Mag. 46, 1873; 48, 1874; Stefan, Wiener Berichte, 1874; 

 97, 1888. Wied. Ann. 38, 1889; Fromme, Wied. Ann. 13, 1881; Ewing and 

 Low, B. A. A. S. Report 1887; Phil. Trans. 180, 1889; H. E. J. G. duBois, 

 Phil. Mag. 29, 1890; Roessler, Elektrotechnische Zeitschrift, 14, 1893; Jones, 

 Wied. Ann. 54, 1895; 57, 1896; Gumlich, Elektrotechnische' Zeitschrift, 30, 

 1909; Peirce, These Proceedings, 44, 1908; Am. Journal of Science, 28, 1909; 

 Weiss, Journal de Physique, May, 1910; Hadfield and Hopkinson, Jour. Inst, 

 Elect. Eng., 46, 1911. 



