254 PROCEEDINGS OF THE AMERICAN ACADEMY. 



ences between the corresponding N's for a rod of 0.3175 cm. diameter 

 and one of 1.905 cms. diameter range from 10 to 16 per cent, both sets 

 of vahies being taken to conform to the conditions stated in (4). 



(6) Most of the rods used in this work have their iV^'s in the range 

 of practical constancy considerably smaller than the values given by 

 Du Bois, but as the diameters of the rods decrease, a very close 

 approach to Du Bois's values is obtained. 



(7) The magnetization is furthest away from uniformity in the 

 region of highest susceptibilities, and becomes more uniform for very 

 low as well as for very high applied fields. 



In conclusion it is my pleasant duty and privilege to thank Professor 

 B. 0. Peirce for suggesting this research and for his constant interest 

 in the work throughout the year. I also desire to state that the 

 astaticised galvanometer system is due to the skill of Mr. John Coulson, 

 Professor Peirce's assistant; and that the construction of the magnetiz- 

 ing solenoid was most successfully carried out by Mr. Thompson, the 

 mechanic of the Jefferson Physical Laboratory. 



Literature on the Demagnetizing Factor. 



J. A. Ewing: "Experimental Researches in ^Magnetism," Phil. 

 Trans., 176, 523-640 (1885). (Plate 57, Fig. 3.) 



A. Tanakadatd : " Mean Intensity of Magnetization of Soft Iron 

 Bars of Various Lengths in a Uniform Magnetic Field," Phil. Mag., 

 (5), 26, 450-456 (1888). 



H. E. J. G. Du Bois : " Zur mathematischen Theorie des Ferromag- 

 netismus," Wied. Ann., 46, 485-499 (1892) (also in "Magnetische 

 Kreise in Theorie und Praxis," Berlin, 1894, p. 37). 



C. R. Mann : " Ueber Entmagnetisirungsfaktoren kreiscylindrischer 

 Stabe," Dissertation Berlin, 1895 ; " Demagnetization Factors for 

 Cylindrical Rods," Phys. Rev., 3, 359-369 (1896). 



Ascoli e Lori : " Sopra il fattore smagnetizzante nei cilindri di ferro," 

 Rendic. R. Acad. d. Lincei, 3:2, 190 (1894); Ascoli: "Sul fattore 

 smagnetizzante nei fasci e nei cilindri di ferro," Rendic. R. Acad. d. 

 Lincei, 6 : 2, 129 (1897). 



Carl Benedicks : " Ueber die Entmagnetisirungsfaktoren kreiscylin- 

 drischer StJibe," Wied. Ann., 6, 726-761 (1901) ; "Sur les facteurs 

 d^magnetisants des cylindres," Bihang Svenska Vet.-Akad. Handlingar, 

 27, (1), No. 4, 14 pp. (1902). 



H. E. J. G. Du Bois : " Entmagnetisirungsfaktoren kreiscylindrischer 

 Stabe," Wied. Ann., (4), ?, 942-943 (1902). 



