HISTORY AND PROGRESS. 



95 



through the lever of the key, and the circuit being thus 

 completed, the current from the z-pole passes through the 

 galvanoscope into the line. 



Xuie 



Fig. 49. 



In the former method (Fig. 48) the operation of the key 

 consists in shifting the line from relay to battery. In the 

 other method, the battery and relay have the same fixed con- 

 tacts 1 and 2 of the key ; but the earth and line change places, 

 the line taking the place of the earth in the former, and the 

 earth being shifted by the key from relay to battery. 



This is by no means so good as the former method, 

 because it necessitates a good insulation of the battery, 

 without which a current, depending on the magnitude of the 

 fault, will not only pass always through the line, but also 

 through the coils of the home-relay; and any accidental 

 contact of the battery with earth will give a signal at the 

 relays of both stations, whilst, with the former method, a 

 similar accident would be entirely without effect further than 

 weakening the currents sent on to the line, notice of which 

 is amply given by the galvanoscope. 



65. Intermediate-station Commutators. Where intermediate 

 stations occur, which are supplied each with only one Morse 



