AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA. 135 
which it originally extended. . . . After the Rolling Downs formation 
had been laid down in the comparatively narrow sea which connected 
the Gulf of Carpentaria with the Great Australian Bight, and converted 
the Australian area into two islands, a considerable upheaval took place. 
The denudation of the Rolling Downs formation then followed, and must 
have gone on for some time. Unequal movements of depression then 
brought about lacustrine conditions on portions of the now upliftod 
bottom of the old deep-sea strait, and in other portions permitted the 
admission of the water of the ocean. Finally a general upheaval placed 
the deposits of the period just concluded in nearly the position in which 
we now find them." 
Jack considers that “ The absence . . . of tertiary marine strata may 
be due to the fact that the elevation which took place after the deposi- 
tion of the upper eretaceous rocks (desert sandstone) placed the whole 
of Queensland above the reach of the ocean during tertiary times." 
(Geol. and Pal. of Queensland, p. 574.) 
These extracts from the past history of Queensland are important, as 
they clearly indicate the great length of time during which the eastern 
extension of the Queensland coast has been exposed to the effects of 
denudation and to the inroads of the sea, — inroads the extent of which 
is clearly indicated by the islands and archipelagos skirting the north- 
east edge of Australia, and the extent of the denudation is plainly vis- 
ible in the shape of the hills and valleys flanking the present coast, line. 
Jack (Geol. and Pal. of Queensland, p. 613) gives the following proof 
of a moderate depression of the Queensland coast: “In the neighbor- 
hood of "Townsville a well reaching to one hundred feet in depth shows 
the presence of clays and gravel belonging to river beds which fringe the 
coast from Cape Palmerston to the mouth of Herbert River. No river 
could possibly have exeavated a channel to this depth while the land 
stood at its present level ; it must have been depressed to or beyond the 
position at which it now stands with referenee to the ocean." 
Fragments of this lost land, he considers, * remain in Fitzroy, Hinchin- 
brook, the Palm and Percy Islands, . . . while a submerged range still 
farther to the east may be represented by the Barrier Reef." 
It seems to me that, in addition to the above mentioned submergence 
of one hundred feet, we must take into account the extensive denudation 
and erosion which Jack himself has so well described in the paragraphs I 
have quoted from him. A denudation and erosion which, acting through- 
out the tertiary period, a period of great fall of water, are of themselves 
quite sufficient to explain the former connection of the islands off the 
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