I4(; CORAL FORMATION. 



cliffs, to the height of half the island ; the greatest 

 elevation of which was 13 feet, with a similar soil, 

 mixed with guano, and filled with burrows of the 

 sooty petrel, or mutton bird. Surrounding it is a 

 low coral reef, trending northward to the outer 

 edge of the group. This reef afforded me an op- 

 portunity of examining the coral formation of the 

 Abrolhos, which, with the exception of Bermuda, is 

 the place farthest removed from the equator where 

 coral formation is found. The reef on which Rat 

 Island rests extends off four hundred yards on the 

 inner side, and has 12 fathoms just off it, on a 

 grey sandy mud. The greater portion is composed 

 of a variety of corals intermixed, and forming a 

 consolidated mass, with brain-stones scattered over. 

 It is nearly dry at low water ; but a portion does 

 not rise so high, projecting out so as to form a 

 narrow shelf, from the edge of which a wall de- 

 scends almost sheer to the depth of 54 feet. The 

 upper 20 feet are formed of a peculiar kind of coral, 

 growing in the shape of huge fans, spreading out 

 from stout stems overlapping each other in clusters, 

 and having angular cavities between. The coral 

 forming the lower 34 feet of the wall is of the com- 

 mon large branch kind. 



Whilst in Good Friday Harbour the quarter- 

 master reported smoke on one of the islands to the 

 north-east. All eyes were instantly turned in that 

 direction, in curiosity to find what could have caused 

 it. And sure enough a lonof streak of smoke was 

 curling upwards through the air. It soon however 



