320 ALEXANDER AGASSIZ 



by what is known of the geology and botany of the 

 mainland and the adjacent islands. Many of the more 

 distant remnants of the former mainland are now mere 

 islets flanked by extensive flats, or they are simply flats 

 eaten away to beneath low-water mark. 



He was thus led to the conclusion that all the flats and 

 reefs lying between the outer line of reefs and the main- 

 land are but the remnants of former islands extending 

 to the eastern edge of the continental plateau, islands 

 which once formed a part of the eastern coast of Queens- 

 land, but which have by erosion and denudation gradu- 

 ally been separated from the mainland and reduced to 

 the flats forming the outer reef flats of the Great 

 Barrier Reef. 



The reports of the Queensland colonial geologists 

 seem to prove that there was a very considerable subsi- 

 dence in Cretaceous times, followed by an elevation of 

 the beds then laid down, as exemplified in the desert 

 sandstones. The outlines of the present coast line and 

 its submarine extension Agassiz took to have been 

 shaped by this subsidence and subsequent elevation, 

 and by the erosion and denudation to which these beds, 

 since their elevation above the level of the sea, have 

 been subjected for so long a period. It is on the upper 

 part of these submarine slopes, of a former geological 

 period, but modified by erosion and denudation up to 

 recent times, that during the present epoch corals have 

 obtained a footing and built up the Great Barrier Reef 

 of Australia. Thus, instead of Jukes's tremendous but- 

 tress of coral, there should be but a comparatively thin 

 veneer of coral rock overlying the denuded land. 



Certain puzzling peculiarities of the reef Agassiz ex- 

 plained as follows : — There is every reason to believe 



