172 
THE TELEGRAPH. 
When shore cables land among rocks, they should be fixed by 
cramps. When the beach is too rugged with rocks, cast-iron 
tubes, divided into two semi-cylindrical parts, are used with 
advantage to surround and encase the cable, so as to preserve 
it from any risk of damage. 
Coral reefs .—In some seas these are a continual danger for 
cables. The coasts of Africa, the Red Sea, and the Australian 
Fig. 112. 
seas, for instance, are so studded with coral reefs that it is 
impossible to avoid them. 
Earthquakes and submarine disturbances. — Interruptions 
from these causes are, fortunately, very rare. But the cable 
between Cagliari and Malta, which passes between Sicily and 
the island of Pantellaria, was in 1858 twice abruptly inter¬ 
rupted, near the isle of Maretino, by the action of submarine 
eruptions ; and in these regions an island has been known to 
be thrown up and to disappear without leaving any trace. 
A submarine convulsion, no doubt of a "volcanic nature, 
