THE SEA-BIRDS. 381 
travel more than 500 miles out to sea, and yet return every 
evening to the islands or rocks where they make their home. 
In fact they scarcely stop even for necessary sleep. They seem 
made to fly and fly for ever. 
Birds are commonly looked upon by mariners as indicating 
land. Old seamen know how to interpret their appearance, and 
are rarely mistaken. The petrel announces the neighbourhood 
of the Cape of Good Hope. The phaeton indicates that the 
tropics are near. The frigates, gulls, and sea-swallows, predict 
according to the direction and height of their flight, fine weather, 
a rough sea, or the rising tempest. The book of Nature is an 
inexhaustible source of instruction. 
