96 THE GREAT BARRIER REEE. 



Adopting the sailing route followed originally b}' H.M.S. Fly and Bramble, and most other 

 craft that have been emploj^ed in making a survey of, and otherwise investigating, the Great 

 Barrier formation, the author proposes to begin examination of this wonderful structure 

 at its southernmost extremity. The first point touched and commented on in Mr. Jukes' 

 narrative is an islet of the Capricorn group, referred to in the text as the First Bunker's 

 Island, but accompanied by a full-page illustration, in which Lady Elliot Island is 

 characteristically figured. This island, which is intersected by the parallel of 24° 5" S., 

 represents the most southern islet of coral formation in the Barrier system. It is also the 

 most southern point in this vast system that is associated with the calcareous conglomerate 

 of which all coral rocks or reefs are compounded. While Lady Elliot Island and the adjacent 

 reefs thus constitute the first area that would be made the subject of a s^^stematic survej-, 

 they also bring to the fore a problem of high interest concerning the actual line of demar- 

 cation of growing reef-corals and reef-formation. It has been a generally-accepted axiom, 

 hitherto, that the formation of reefs is indissolubly associated with the life, growth, and decay 

 of a certain class of corals that are universally distinguished as reef-corals. Wherever the 

 conditions favour the growth of those specific forms of coral, there also, is it commonly 

 held, coral-reef formation must be in progress. The two phenomena, however, the author 

 is in a position to demonstrate, are not necessarily concurrent. 



The limit of distribution of typical reef-forming corals, and their more abundant disintegrated 

 residua, extends, as a matter of fact, considerably to the south of Lady Elliot Island, but without 

 giving rise to a trace of reef-formation. In Moreton Bay, at the present daj^, masses of the dead 

 coralla of at least two species of Madrepora, the one a shrubby type allied to M. dccipicns, and the 

 other a corymbose species most nearly resembling M. convexa or M. niillcpora, may be collected 

 at low spring-tide in the vicinity of Mud Island. These Madreporae, it should be observed, 

 are all in situ, just as they originally grew, and are covered by from one to two or three feet of 

 water only, at ordinary low spring-tides. Associated with these dead Madreporae there in many 

 instances occur the living coralla of certain other species, and among them, more especially, a coral 

 differing apparently in no essential respect from the Red Sea variety, Favia Ehrenbcrgii. This 

 Astraeaceous coral forms sub-spheroidal massive colony-stocks, varying from a few inches to two 

 feet or more in diameter, such larger coralla often weighing over one hundredweight. The 

 author collected, more rarely interspersed among these Faviae, small living coralla of a Porites, 

 and of a species of Psammoseris. In the earlier days of the colony, thirty or forty years ago, 

 these Moreton Bay corals, including, more particularly, the massive Faviae, were systematically 

 collected, in barge-loads, for the purpose of making lime. By these means, beyond doubt, 

 the original abundant growth of coral in this special area has been materially diminished. 



Moreton Bay is of considerable dimensions ; its e.xtreme length, from Caloundra in the 

 north to Southport in the extreme south, being no less than one hundred miles. It is practically 



