PROFESSOR CHRYSTAL ON THE DIFFERENTIAL TELEPHONE. 629 
The following table, calculated for R=6, S=14, L+N=:004, will show the 
dependence of the ratio € : & upon n:— 
n 10° 10° 10’ 108 10° to 
& 2-37 | 2-24 | 1-62 | 113 | 1-01 | 1-00 
al 
The condition for & > &, is 
(2N —L)(2N + L)n?+S?—R?> 0. 
For iz > a , " 
(QN -L)@2N+L)n2—R(R+5)>0. 
These formule explains the results above described. 
The following theory includes experiments 4 to 7 :— 
Fig. 5. 
Let the current strength, resistance, and self-induction of the main and 
neighbouring circuits be «RL, ySN respectively, their coefficient and mutual 
induction M, and let there be a condenser of capacity X in the neighbouring 
circuit. 
Then (LD + R)v+MDy=Asinnt , 
MD*2+(ND?+8D+x)v=0 : 
(a+ BD + yD? +8D9)2= A(x + SD +ND?)sinat , 
(a+ BD+yD?+68D?)y= —AMD?sinnt , 
where 
