considerable bulk with weight. South of Hatteras, where stones

are scarce, the sand dredged from parts of the channel was filled

into the crib, the surface of which has a concave metallic cover,

a trough of still water being often the best barrier against the

passage of waves. This double coast-line has been a great

benefit, and propelled vessels of moderate draught can range in

smooth water, carrying very full loads, from Labrador to the

Orinoco. The exits are, of course, protected by a line of