494 KEELING ISLAND 



of the Astrolabe, that an Actinia or sea-anemone, as well as a 

 flexible coralline allied to Sertularia, both possess this means 

 of offence or defence. In the East Indian sea a stinging sea- 

 weed is said to be found. 



Two species of fish, of the genus Scarus, which are common 

 here, exclusively feed on coral ; both are coloured of a splendid 

 bluish-green, one living invariably in the lagoon, and the other 

 amongst the outer breakers. Mr. Liesk assured us that he had 

 repeatedly seen whole shoals grazing with their strong bony 

 jaws on the tops of the coral branches ; I opened the intestines 

 of several and found them distended with yellowish calcareous 

 sandy mud. The slimy disgusting Holothuriae (allied to our 

 star-fish), which the Chinese gourmands are so fond of, also 

 feed largely, as I am informed by Dr. Allan, on corals ; and 

 the bony apparatus within their bodies seems well adapted for 

 this end. These holothuriae, the fish, the numerous burrowing 

 shells, and nereidous worms, whicli perforate every block of 

 dead coral, must be very efiScient agents in producing the fine 

 white mud which lies at the bottom and on the shores of the 

 lagoon. A portion, however, of this mud, which when wet 

 strikingly resembled pounded chalk, was found by Professor 

 Ehrenberg to be partly composed of siliceous-shielded infusoria. 



April \2th. — In the morning we stood out of the lagoon 

 on our passage to the Isle of France. I am glad we have 

 visited these islands : such formations surely rank high amongst 

 the wonderful objects of this world. Captain Fitz Roy found 

 no bottom with a line 7200 feet in length, at the distance of 

 only 2200 yards from the shore; hence this island forms a 

 lofty submarine mountain, with sides steeper even than those 

 of the most abrupt volcanic cone. The saucer-shaped summit 

 is nearly ten miles across ; and every single atom,^ from the 

 least particle to the largest fragment of rock, in this great pile, 

 which however is small compared with very many other lagoon 

 islands, bears the stamp of having been subjected to organic 

 arrangement. We feel surprise when travellers tell us of the 

 vast dimensions of the Pyramids and other great ruins, but how 

 utterly insignificant are the greatest of these, when compared 



1 I exclude, of course, some soil which has been imported here in vessels from 

 Jr.ilacca and Java, and likewise some small fragments of pumice, drifted here by the 

 waves. The one block of greenstone, moreover, on the northern island must be 

 excepted. 



