154 SMALL VOLCANIC CltOUP. 



varies from ten fathoms by more than a fathom or 

 two over the whole distance from the coast of 

 Australia to that of New Guinea. The north-west 

 portion of this band of islands has not yet been 

 examined ; but north of Banks's Islands and Mul- 

 grave Islands there appears to be a large patch of 

 true coral reefs in which the Hormuzeex and Ches- 

 terfield got entangled in 1798. The eastern limit 

 of this central band, however, is very well defined 

 by a line running a little east of north from Mount 

 Adolphus, and just east of Harvey *s Rock, Saddle 

 Island^ and Turtle-backed Island* To the east of 

 this line there are no islands in which any such rock 

 as porphyry or sienite occurs; but all are low coral 

 islands, scarcely raised above the sea ; and multi- 

 tudes of true independent coral reefs of great extent 

 are scattered about with considerable apparent irre- 

 gularity. Having traversed these for sixty miles 

 towards the east, we again come to a few high and 

 rocky islands, namely, the three Murray Islands 

 and Erroob or Darnley Island. These, however, 

 are volcanic islands, consisting principally of lava. 

 Another low island to the north of these, called 

 Bramble Key, or Caedha, has likewise a patch of 

 volcanic rock in its centre, and another not far 

 from it. 



Of the rocky islands occurring in the central 

 north and south band of Torres Strait, some are 

 inhabited and some not, or only occasionally so. 

 All those permanently inhabited, and at a distance 



