Mr. H. A. Rowland on Magnetic Distribution. 351 



Assuming that fi is variable, the formula indicates the same 

 change that we observe ; for as Q" increases from zero upwards, 

 fM will first increase aud then decrease; so that as we increase 

 the magnetizing force from zero upwards, the curve should first 

 decrease in steepness and then increase indefinitely in steepness. 

 In these Tables the decrease of steepness is not very apparent, 

 because the magnetization is always too great ; and indeed on this 

 account it is difficult to show it; but in Tables V., VI., and VII. 

 this action is shown to some extent by the values of r in the for- 

 mulae. The change of distribution with the helix arranged in 

 this way at the centre of the bar is greater than in almost every 

 other case, because the magnetism of the bar, Q", can change 

 greatly throughout the whole length of the helix, and thus the 

 value of r be changed, and so the distribution become different. 



The next case of distribution which I shall consider is that of 

 a very long rod having a helix wound closely round it for some 

 distance at one end. 



Table X. is from a bar 9 feet long with a helix wound for one 

 foot along one end. The bar was \25 inch in diameter. All except 

 the first column is the sum of two results with the current in 

 opposite directions, and after letting the bar stand for some time, 

 as indeed was done in nearly every case. The first column con- 

 tains twice the quantities observed, so as to compare with the 

 others. The zero-point was at the end of the bar covered by the 

 helix. 



Table X. 





A. 



B. 



C. 



D. 



x and L. 













•245. 



•360. 



•600. 



1-09. 





 1 

 2 

 3 



i 



5 



S 



8 

 9 

 10 

 11 

 12 

 13 

 14 

 15 

 16 

 18 

 20 

 24 

 36 

 48 



+ 17-6 



4-29-4 



4-52-0 



4-1087 



4- 96 



4-168 



4-31-5 



4- 60-1 



4- 7-4 



4-131 



4-24-3 



4- 45-8 



4- 5-4 



4- 9-8 



+ 191 



4- 341 



4- 3-4 



4- 7-2 



4-147 



4- 22-8 



4- 20 



4-4 6 



4- 9 9 



4- 16-0 



4- 0-6 



4- 2-4 



4- 5-4 



4- 9-6 



- 0-8 



+ 0-3 



4- 12 



4- 0-6 



- 1-8 



- 1-6 



- 21 



- 03 



- 30 



- 3-6 



- 66 



- 8-8 



- 50 



- 63 



- 8-6 



- 156 



- 74 



-100 



-16-4 



- 27*1 



- 8-4 



-100 



— 16 9 



- 26 5 



- 6-0 



- 79 



-14 5 



- 22-6 



- 52 



- 70 



-12-5 



- 21 





- 5-3 



— 119 



- 190 





- 9-4 



-191 



- 31 2 





- 5 3 



-15-2 







- 65 



-19-3 









- 5-6 



- 07 



- 60 



- 1-2 





