TELEGRAPHIC APPARATUS. 
261 
to reach suitable ground. In the island of Saint-Pierre 
Miquelon, the earth connection had to be made some distance 
out at sea. Ordinary methods proved insufficient, and the 
mirror apparatus of one station of the Brest cable showed the 
Morse signals of an American cable belonging to a different 
company. This was in consequence of an inductive action, 
arising from the general dryness of the soil of the island. 
A 1 A 2 A 3 A 4 
P 
Fig. 184. 
At places where there are submarine cables, no better earth 
connection than that provided by the outer metallic sheathing 
can be found anywhere. For these wires are in contact 
with sea and land throughout their whole length, and they 
form what may be called a return line for the currents. At 
railway stations, an excellent earth connection is found in the 
rails. 
Lightning Conductors .—Thunderstorms and atmospheric 
electricity would often destroy telegraphic apparatus if they 
