204 PIERCE. 



By the use of (13), this condition (26) becomes 



M = Xi/10, (28) 



and by (8) and (28) equation (22) gives 



T = VlC2 = Vl.2L,C2- (29) 



Equation (28) gives the value of the Mutual Inductance M to be intro- 

 duced between the adjacent series coils of Self Inductance Li {and of 

 negligible resistance) in order to make the time-retardation T per section 

 be as nearly as possible independent of the frequency and to have over a 

 xvide range of frequencies approximately the value given in (29). 



// the resistance of the coils is not negligible it is possible to modify the 

 relation {28) slightly in a manner that will enhance slightly the constancy 

 of T over a given range of frequencies, but in practice, where a reasonable 

 effort is made to keep resistances small, the relation {28) is sufficiently 

 accurate. 



In any case the exact value of T can be calculated by the use of {17) and 

 (8). 



11. Computed Table and Curves Showing the Performance 

 of a Line with Mutual Inductance Equal to One Tenth of Self 

 Inductance in Comparison with a Line of Zero Mutual In- 

 ductance. — Table I of which four columns were computed from 

 the exact Equation (17) with the use of (8), gives the values of 



T jy/LCi for different values of my/LCi. 



