H. A. Rowland — Studies on Magnetic Distribution. 



Plot of Table X. 

 In fig, 4 we have a plot of the results found for this bar. 

 The curves are such as we should expect from our theory 

 except for the variations introduced by the causes which we 

 have hitherto considered. Thus the sharp rise in the curve 

 when near the ehd of the bar has already been explained in 

 vith Table III. A small portion of it, however, is 

 • those lines of induction which pass out through the end 

 1 of the bar, and in future experiments these should be 

 [ and allowed for. When considering surface-density 

 we should also allow for the direct action of the helix, though 

 this is always found too small except in very accurate ex- 



To estimate the shape of the curve theoretically in this case, 

 let us take equation (4) once more, and in it make s' = cd and 

 s"=V'RR' which will make it apply to this. We shall then 

 have A'=—l, and A'''=QO. 



Whence for the positive part of Q'% we have 



'2RV 



and for the negative part 

 therefore the real value is 

 And if X is reckoned from the end of the rod, we have 



~2R'/ 

 When x=0, this 



becomes 



