,oo THE GREAT BARRIER REEF. 



considerable, and may endure for a lengthened period. Within recent years, and notably in 

 1887, the floods were so heavy and of such long duration that even the oysters were destroyed 

 wholesale. This fact furnishes, in itself, a ready clue to the extinction of the Madreporce ; these 

 corals, being very impatient of any admixture of fresh water, succumbed, in all probability, 

 under the influences of the first abnormally heavy flood that occurred after the free access 

 of the sea became impeded by the accumulated sand-bars. The survival and continued 

 growth of the massive Faviae is explained by the fact that they represent a species that can 

 thrive in water of much less dense specific gravit}' than the essentially oceanic Madreporae. 

 The same explanation applies to the Porites and Psammosens found growing, sparingly, in its 

 vicinity. This one area, off Mud Island, where they still survive, constitutes the last remaining 

 locality favourable to the growth of these most southern outpost representatives of the Great 

 Barrier reef- though reefless-corals, it possessing the freest communication, under existing 

 conditions, with the waters of the open sea, combined with immunity from the deleterious 

 influences of shifting sand. 



Northwards from Moreton Bay, there is one other coral-producing area that demands brief 

 notice. This is Harvey Bay, which intervenes between the mainland and the long irregular 

 island known as Great Sandy or Eraser Island. This bay is contracted at its southern 

 extremity into a narrow strait, but widens out and is entirely open to the sea towards the north. 

 Sandy Island, as its name denotes, is composed, like the islands flanking Moreton Bay, almost 

 entirely of drifted siliceous sand ; and there is but little ground within the confines of 

 Harvey Bay that is suitable for coral-growth. Among a small assortment that has been 

 obtained from the northern extremity of the bay, a species of large-celled Turbinaria is 

 most abundantly represented. Members of this same generic group, it is worthy of remark, 

 constitute the dominant representatives of the Madreporarian class in the vicinity of Sweer's 

 Island, in the Gulf of Carpentaria, where the water in winter is occasionally below the 

 tropical isotherm of 68'^. 



Great Sandy, or Fraser Island, as it is otherwise known, is fully one hundred miles in length. 

 Towards its southern moiety it encloses the famous oyster-growing area, known as Wide Bay, 

 into which the Mary River falls. Its northern end is the promontory of Sandy Cape, about 

 400 feet in height, from the foot of which projects seawards that long tongue-like bank of 

 submerged sand over which the sea is continually breaking, which received from Captain Cook 

 the name of " Break-sea Spit." In the Admiralty charts this sand-spit is set down as being 

 composed of sand and dead coral. In earlier days, when the Madreporae flourished in 

 Moreton Bay, a bank of growing coral, apparently, occupied this site. At the present day, 

 not only has the living coral vanished, but its dead remains have been engulphed in sand. 



There are one or two facts of interest that invite record in association with Sandy or 

 Fraser Island. In close vicinity to the lighthouse, at its north end, examples of apparentl3' 



