Mr. H. A. Rowland on Magnetic Distribution. 



Table IV. 

 Bar -19 inch diameter. at centre of bar. 



273 



L. 



Q'e. 



Ob- 

 served. 



Q'e. 



Cor- 

 rected. 



Q'. 



Cor- 

 rected. 



R' 



1 _R' 



r 2 R 



2 



3 



4 



5 



6 



7 



8 



9 

 10 

 11 

 12 

 13 

 14 

 15 

 28£ 



24-0 

 170 

 13-7 

 11 6 



10-2 

 9 

 8-0 

 71 

 64 

 5-7 

 4-9 

 4-4 

 3-6 

 33 



22-4 



240 

 170 

 13-7 

 11-65 

 1015 

 90 

 80 

 715 

 635 

 5-65 

 50 

 4-4 

 3-9 

 3-4 

 224 



151-7 

 1277 

 110-7 

 970 

 85-4 

 75-2 

 662 

 58-2 

 511 

 44-7 

 391 

 341 

 29-7 

 25-8 

 22-4 



041 

 •0256 

 0192 

 0168 

 •0150 

 0142 

 0150 

 0159 

 •0160 

 0167 

 •0180 

 •0184 

 0184 



244 



391 

 521 

 595 

 667 

 70-4 

 667 

 629 

 62-5 

 59-9 

 55-6 

 54-3 

 54-3 



On looking over column 6, which contains the values of 



1 R' 



-^= p- =BIa/jb (equation 7), we observe that as Q' decreases, 



the value of Wa/x first increases and then decreases. Now it is 

 not probable that R' undergoes any sudden change of this sort ; 

 and so it is probably due to change in the permeability of the 

 rod. Hence by this method we arrive at the same results 

 as by a more direct and exact method*". But by this means 

 we are able to prove in the most unequivocal manner that 

 magnetic 'permeability is a function of the magnetization of the 

 iron and not of the magnetizing force. Hence it is that I have 

 preferred, in my papers on Magnetic Permeability, to consider 

 it in this way in the formulae and also in the plots, while 

 Dr. Stoletow (in his paper, Phil. Mag. January 1873) plots 

 the magnetizing-function as a function of the magnetizing force. 

 When we plot the results in this Table with reference to 

 Q' and Wojjl, the effect of the variation of R' is apparent; and 

 we see, on comparing the curve with those given in my paper 

 above referred to, that R' increases as L increases, at least 

 between L = 2 and L = 8, which is as we should suppose from 

 the arrangement of the apparatus. For this Table I happen to 

 have data for determining Q in absolute measure ; and these show 

 that the maximum value of //, should be about where the Table 

 shows it to be. 



* Phil. Mag. August 1873. 

 Phil. Mag. S. 4. Vol. 50. No. 331. Oct. 1875. 



T 



