328 ELEMENTS OF ELECTRICITY AND MAGNETISM. 



the steady current excites the neutral relay, the lever of which 

 pushes a strip of paper against the type wheel and prints the 

 letter A. When the key at the sending station is raised, the cur- 

 rent reversals begin again, the type 

 wheel at the receiving station starts, 

 and at the same time the lever of the 

 neutral relay falls back and actuates a 

 device which moves the strip of paper a 

 step forward for the printing of the 

 next letter. 



Fig. 30. 



34. Submarine telegraphy. Figure 

 30 shows a full-size sectional view of a 

 submarine telegraph cable. The con- 

 ductor at the center consists of a number of strands of copper 

 wire. Surrounding this is a layer of gutta percha, and the whole 

 is protected by a covering of tarred hemp and steel wire. 



\ 



2 



Fig. 31. 



The conductor and metal sheath of the cable, together with 

 the intervening insulator, constitute a condenser of large electro- 

 static capacity. The effect of this large electrostatic capacity is 



