Variable Mutual Inductances. 
171 
As an example, in fig. 15 are given three scales for h = 5*5, 
p—5'5; h = 7, p = 7'2; and 7* = 10, p=4*2 respectively, when 
A =10, a = 5, 6 = 5, and t^ n 2 === 33,000. 
Although these scales give very different ranges, the 
general characteristic of all three is an openness at both 
ends; no proportions that I have tried tend much to make 
the scale uniform throughout. The openness at the lower 
values is a distinct advantage, however, when dealing with 
Fig. 15. 
30 
izr 
IQ.5 
loo 
small inductances ; but care must be taken, when marking 
that part of the scale, that the subdivisions shall be accurately 
marked and not put in merely by interpolation. 
Scale (2) in fig. 15 is the best of the three and is nearly 
that which I have used in practice. 
In conclusion I desire to express my best thanks to 
Dr. Glazebrook, for his kind encouragement and valued 
advice. 
Sept 21, 1907. 
