AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA. 143 
coast of Australia had “not suffered any depression during a long period 
of time,” yet considered this no valid objection to Darwin’s theory, “ be- 
cause previously to this time depression might have been taking place 
throughout a far more extensive period.” This statement seems to me 
to open a totally different question from that originally considered by 
Darwin. We are now called upon to decide upon the continuity of the 
coral reefs of to-day with reefs which must have had their origin within 
the tertiary period. If this continuity has existed, the reefs of the ter- 
tiary period, as far as we know them from their fossil representatives, 
differed greatly from the reefs of the present epoch, which Jukes has 
characterized as “the coral age of the globe." ! 
That such a depression as is required by the Darwinian theory of 
coral reefs has actually taken place over the greater part of Northeast- 
ern Australia, no geologist will deny. But it is a depression which dates 
back to the cretaceous period, and surely we cannot claim that the corals 
which underlie the Great Barrier Reef of to-day began to grow along the 
cretaceous shores of Northeastern Australia at the time when this great 
depression began, and that they have a thickness which should corre- 
spond to a depression of at least 2,000 feet. There is nothing in the 
known configuration of the coast of Queensland, as shown by the hy- 
drography, to warrant such an inference. 
Krämer? has also pointed out the irrelevance of introducing questions 
of secular elevation or depression into the discussion of the formation of 
coral reefs. His review of the subject, as far as it relates to the coral 
reefs of the Samoa Islands, is on entirely different lines from the discus- 
sion of the theory of Kent, who was writing in great part in a popular 
manner, and often adopted arguments which he must have expected his 
readers “of necessity to skip."? That the theory of subsidence to ac- 
1 Voyage of the “Fly,” Vol. L. p. 848, and Murray, John, Trans. R. S. Ed, 
XXX VIII. No, 10, p. 491. 
2 Ueber den Bau der Korallenriffe, p. 36. See also A. Agassiz, Bull. Mus. Comp. 
Zočl., Vol. XVII. No. 3, 1889, p. 131. 
3 Tt is unfortunate that in his general discussion of the theory of coral reefs 
Kent should not have been more accurate, and have revised the statements of the 
older writers he quotes, in the light of the more recent publications on coral reefs. 
We certainly know enough of the topography of the Marshall and Caroline Islands 
to show the inaccuracy of the following statement: “The respective superficial 
areas of the Low, Marshall, Caroline, and Maldive archipelagos, none of which 
contains an islet which rises above the height to which waves and wind or open 
sea can heap up matter.” The statements of Darwin regarding atolls of the West 
Indies, and the characteristics of some of the banks in the same district, which 
Darwin obtained at second hand, are repeated again, although enough has been 
written on the West Indian coral reefs to show what these banks and atolls really 
are. 
