Chap, v.] 



MIGRATION OF PENGUINS. 



115 



not visible from any great distance ; the birds cannot move 

 through the water with anything approaching the velocity of 

 birds of flight ; they have, however, the advantage of a constant 

 presence of food. The question of the aquatic migration of 

 penguins and seals seems a special one, and presents quite 

 different difficulties to that of the migration of birds of flight. 

 The penguins certainly do not go to the Cape of Good Hope 

 nor St. Helena, and they cannot live at sea altogether. 



The migration of the turtles at Ascension Islands seems to 

 be possibly a parallel case. The young turtles on leaving the 

 egg go down to the sea and disappear, returning only when full 

 grown to breed ; this is the account given by residents. If 

 they do really leave the neighbourhood of the island, there 

 seems no possible means by which they can find their way 

 back. 



There is little fresh water on Nightingale Island. I saw one 

 pond in the rookery, but the 

 water was undrinkable. In 

 a cave, however, where we 

 landed, there was a scanty 

 trickling spring of excellent 

 water filling a small basin ; 

 water enough to keep three 

 or four persons alive might be 

 got here. 



We left Nightingale Island 

 in the evening, and made for 

 the Cape of Good Hope. 



Besides the birds I have 

 mentioned, the great Albatross 

 {D. exida7is) breeds at Tristan 

 da Cunha, and on the top of 

 Inaccessible Island. At Tris- 

 tan da Cunha it nests actually 

 within the crater of the termi- 

 nal cone around the lake, 7,000 

 feet or more above the sea. 



The Mollymauk is common in Tristan da Cunha, and its 

 eggs were brought off to us by the islanders for sale ; they are 

 not bad eating. Cape pigeons {Daption cape?tsis) and the 

 Giant-petrel {Ossifraga giganfea), nest in Tristan da Cunha, 

 and one specimen of Procellaria glacialoides was obtained on 

 shore by Von Willemoes Suhm. 



There are two land shells of the genus Balea allied to pupa ; 

 an Oniscus, three small Curculios, four Geometire, a Hippobosca, 

 Mtisca, and Tipie/a, mentioned by Captain Carmichael as found 



GREAT ALBATROSS, DIOMEDEA 

 EXULANS. 



