STUDIES ON MAGNETIC DISTRIBUTION 



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extend beyond the helix, but not nearly so well as in this case, seeing 

 that here Q" can obtain a greater value. 



Assuming that /u is variable, the formula indicates the same change 

 that we observe; for as Q" increases from zero upwards, ft will first 

 increase and 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 



TABLE x. 



values of r in the formulae. 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 



