412 RAMBLES OP A NATUEALIST. [Ch. XXIV. 



The voyage across the Indian Ocean, from Java Head to 

 the South African coast, was long and uneventful. As we 

 approached the coast large numbers of sea birds almost con- 

 stantly accompanied the ship, of which perhaps the most 

 common was the fork-tailed petrel (Thalassidroma Leachii). 

 The first time I observed them was 1300 miles west of Java 

 Head, where the only intervening land was the Keeling 

 Islands. They flew about the ship's wake, skimming over 

 the crests of the waves, and evidently quite at ease ; every 

 now and then putting out their legs as though touching the 

 surface, or running along the water. Night and day they 

 followed the ship for weeks together, never appearing to rest. 

 But whence they come, where they live, how they sleep or 

 rest, is a mystery. If on the water, why are they not snapped 

 up by predaceous fish ? That some of these birds are of 

 nocturnal habits is proved by the fact that I have seen, when 

 24 hours' sail from Ascension, a bird hovering over the ship 

 in the moonlight, sailing to and fro across the moon's disc, 

 for some hours, and that when no birds had been observed 

 about the ship for some days. Tropic birds (Phaethon) also 

 made their appearance in long. 62° E., and lat. 23J° S., when 

 we were 17 or 18 days distant from land in either direction. 

 But when near the South African coast the fork-tailed 

 petrels were accompanied by the sooty petrel, or Cape hens 

 (Puffinus major). Cape pigeons (Daption capense), moUy- 

 mawks (Diomedea chlororhynchus), whale-birds, and even 

 gaimet (Sula capensis), which last I observed at least 70 

 miles from land. When, however, we were blown oif the 

 coast by a north-wester, the fork-tailed petrels, and moUy- 

 mawks, or yellow-billed albatross, were the only birds which 

 seemed at home in the gale. The latter are siugularly 

 graceful in their flight. They swim well and rapidly ; and 



