312 TORRES STRAITS. 



Wednesday Island, Torres Straits, Sept. 8th, 1874. — We 



left Cape York on September 8th, and made for the Prince of 

 Wales Passage through Torres Straits. I landed at Wednesday 

 Island, a distant outlier of Cape York, which, with Hammond 

 Island, is passed close by in the track through the passage. 

 The island is about two miles long, it is made up of quartz 

 porphyry, forming hill masses, a couple of hundred feet or so 

 in height, with sandy flats at their bases. 



In places, the hill slopes come right down to the sea, 

 forming small headlands, and here the beach is composed of 

 boulders with small stretches of quartz sand derived from the 

 rocks between them. Along a wider bay to the north, the 

 whole beach is made up of calcareous sand and broken and 

 dead shells. A shore platform reef extends all along this side 

 of the island ; in some places it is made up of consolidated 

 coral rock, full of large masses of dead corals cemented together 

 with coral mud, which masses are at its margin seen projecting 

 here and there between muddy pools of water. 



In other places the coral rock passes gradually into regular 

 mud flats. There were very few living corals indeed about the 

 shore platform ; it required careful searching to find them. I 

 found only the species of Euphyllia, which was at Somerset, and 

 a small Ash-cca. One large mass of Astnea thrown up by the 

 waves and embedded in the mud, had a small patch on one 

 side of it still alive, the rest was quite dead. 



Though stony corals were so scarce, soft Alcyonarians were 

 in great abundance. The rock was full everywhere of the 

 Giant Clam {Tridacna), the largest bivalve shell which has 

 ever existed, a familiar adornment of fountains and oyster-shops 

 in England. This mollusk lives sunk in a cavity of its own in 

 the rock, with only its brilliant blue or green mantle fringes 

 showing and betraying its retreat. These protruded mantle 

 lobes have the appearance of huge expanded elongate sea 

 anemones, and at first sight one takes them for such. The 

 shells must be quarried out of the rock with a hammer and 

 chisel if they are wanted. 



The main peculiarity of these coral flats, as at Somerset, is 

 their extreme muddiness and the small quantity of life about 

 them. A Sargassum grows abundantly on the rock masses, 

 with several other algas. No doubt it is the decomposition of 

 these and the soft Alcyonarians which renders the coral mud 

 so dark and slimy. The occurrence of beaches of calcareous 

 and siliceous sand close together, both rising from the same 

 coral flat, is an interesting fact, as showing how easily beds of 

 such very different materials may become associated or super- 

 posed. A large Chama shell is very abundant, cemented to 



