SHUDDEMAGEN. — DEMAGNETIZING FACTORS FOR IRON RODS. 245 



This shows again how greatly different results obtained by step and 

 reversal methods can be, if the observations are not properly corrected 

 by using the appropriate N. 



Distribution of Magnetic Induction. 



In our theoretical discussion of the shape of the iY-curves we found, 

 page 197, that we might expect that the magnetization is much nearer 

 uniformity when the applied field H' is quite small, than it is in the 

 region of large susceptibility. Now several articles have been published 

 on the distribution of magnetic induction in iron rods,^^ but the mag- 

 netizing fields which these writers used were of much greater strength 

 than are necessary in order to investigate this particular question. 

 However, Benedicks ^^ found a very neat inverse relation between the 

 susceptibility k and the pole-distance» in a short bar magnet. This is 

 very clearly shown by Figure 21, which has been reproduced from his 

 article. The curve called "Distance des Poles " has the ordinates l/L, 

 where L = actual length of the bar magnet, and / = distance between 

 poles, the method of determining / being based on the formula 



t* -*mean 



/n, 



19 Phil. Mat;., (5), 46, 478-494 (1898), " On the Distribution of Magnetic Induc- 

 tion in Straight Iron Kods," J. W. L. Gill; Phil. xMag., (5), 48, 262-271 (1889), 

 " On the Distribution of Magnetic Induction in a Long Iron Bar," C. G. Lamb. 



20 Journ. de Physique, (4), 1, .302-307 (1902), "Etudes sur la Distance des 

 Poles des Aimants " ; Bihang Svenska Vet.-Akad. Handlingar, 27, (1) No. 5, 

 23 pp. (1902), " Untersuchungen iiber den Polabstand Magnetischer Zylinder." 



