STUDIES ox MAGNETIC DISTRIBUTION 

 therefore the real value is 



Q,, _ &AL f ( Z _ b} , b _ o\ , f -rx\ . 



U< ~ 2R'r C 

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



113 



(10) 



When x = 0, this becomes 



and when x = b, it becomes 



the ratio of which is 



and this is the ratio of the values of Q" at the ends of the helix. 

 When & is 12 inches, as in this case, we get the following values of this 

 ratio : 



To compare this with our experiments, let us plot Table X once more, 

 rejecting, however, the end observations and completing the curve by 

 the eye, thus getting rid of the error introduced at this point. We then 

 find for this ratio, according to the different curves, 



B. C. D. 



2-1 2-3 3-2 



It is seen that these are all above the limit 2, as they should be 

 though it is possible that it may fall below in some cases, owing to the 

 variation of the permeability. As the magnetization increases, the 

 values of the above ratio show that r decreases, as we should expect it 

 to do from the variation of /*. 



To find the neutral point in this case, we must have in formula (10) 



