ft . - 



HISTORY AND PROGRESS. Ill 



printing-beam of M from the contact screw 1. When the line 

 current in L stops, the tongue of the relay R 2 falls back on 

 the insulated rest 1, the local circuit is interrupted, and the 

 beam 3 of M returns to the reposing contact 1. The beam 

 of the spacing-apparatus s is, however, not released at the 

 same moment, because the current of the polarisation battery 

 i has quickly reversed the magnetism of the coils of s, before 

 the armature had time to get away. And a negative cur- 

 rent immediately following the positive one, by the line 

 L, deflects now the bar of the other relay, R L , which closes 

 that part of the local circuit containing the spacing' apparatus 

 only. The beam of s is therefore retained during the con- 

 tinuance of this current, and a negative current passes into 

 the down-line from E z (w%, contact 1 and beam of s, contact 



1 and beam 3 of M, to c\, 2 G D 1) to L X . 



On the interruption of this negative line-current in L, the 

 polarisation battery performs its functions again. 



When the translation is from the down to the up-line, the 

 connections remain precisely the same ; the Morse spacing- 

 apparatus, and relays, however, are in action on the other 

 side, whilst those on the left become passive. 



Signals are given to the line L by turning the switch Cj on 

 1, and c n on 2. The positive current given by pressing 

 down the key, then goes in the circuit E, c, w, 1, and 2 (of 

 key) % 2, q 1, G 1, L ; the negative, when the key rests on 

 the reposing contact 3, passes in the direction E, z, w s , 3 and 



2 (of key) c n 2, c x 1, G 1, L, &c. 



To receive from the same side, q is put on contact 1, and 

 c n on 1. The arriving current from L goes through G 1, 

 q 1, c n 1, w^ coils of both relays, w 2 , G 2 , and earth. When 

 the arriving current is positive, it deflects the bar of relay 

 R 2 , and closes the local circuit of the Morse and spacing 

 apparatus ; when negative, in deflects the bar of R X , and closes 

 the local circuit of the spacing apparatus only. 



73. Static Induction in Submarine and Subterranean Lines. 

 It has already been explained that the outside of a Leyden 

 jar becomes charged by induction when the interior coating 

 is charged by contact with some source of static electricity ; 



