of Duplex Telegraphy. 129 



in two; one part goes through a! and the other through g' to 

 earth. 



Further, n „ _,.. m" 



C"=E" 



N » J 



where 



," =/ (S" + a"') + a"'(a'' + iH ). 



/a' 



»'+/'+/>' 



/'(a' + &')+«'(«' + «") 



and N M an expression identical in form with N'. 



Farther, by Q' we understand the force which acts on the 

 receiving-instrument of station I. when both stations are send- 

 ing simultaneously : duplex signals. 



This force is again proportional to the current which, under 

 these circumstances, passes through the receiving-instrument g { 

 of station I. 



This current can be expressed by 



and therefore 





Qf-ocE'-.— o>', 



n' r 



o' being the current actually in the line at point 1 when both 

 stations are sending simultaneously ; and this current, being the 

 algebraical sum of two currents, may be either + , 0, or — . 

 We will suppose that a' contains the sign itself. 

 Further, we have 



,_ EW EV , 

 a ~ N' N" hi) 



ni=(b' + d ! +f')(a' + g<)+b'(f> + d'); 

 and ft is a function which becomes identical with ^ if we put 



Therefore the two functions D and S are for the bridge me- 

 thod (station I.) most generally expressed as follows : — 



E'N^l A' 



- E"JN' fi! m'W {lll -> 



Phil. Mag. S. 4. Vol. 48. No. 316. Aug. 1874 K 



