AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA. 199 
the air and sun. Іп both instances the exposure was due to the force 
of the gale at low tide driving the water off the flats upon which the 
Madrepores were growing. Опа later occasion, a similar gale lasting 
'longer completely destroyed this field of Madrepores. 
During a visit which I paid to the Bermudas, the extensive reef 
patches covered with living corals within the outer lagoons were exposed 
at an extremely low stage of tide during the time we were steaming out 
of the Bermudas on our way to New York. It is very evident that in those 
coral reef regions of the Pacific where there is a great range in the rise 
and fall of tide, it is not unusual to have great stretches of coral reef ex- 
posed at low tides, if wo may judge from the photographs of a coral reef 
exposed on the weather side of Levuka (Fiji Islands) which is on exhibi- 
tion in the coral gallery of the British Museum, from similar photographs 
from the Hebrides in the coral gallery of the American Museum of Natural 
History in New York, and from a photograph of a Madrepore reef on the 
lee side of Apia published by Krämer 
The description which is given by Jukes (Voyage of the “ Fly," 
Vol. I. p. 314) of one of the reef flats of the Great Barrier Reef is a most 
admirable description of the average reef flat. characteristic of the Aus- 
tralian coral belt. Ав Kent has not reprinted this account, I here 
reproduce his description of what I have called a “reef flat or reef 
patch" ;— 
** The size and form of an ‘individual coral reef? is perfectly indeterminate; 
it may be circular, oval, or linear; its surface may vary from a mere point to 
an area of many square miles. Those, however, which occupy the extreme 
edge of a mass of reefs (there is a term wanted to express the distinction be- 
tween an individual reef, unbroken by any deep water channel, and a group of 
such reefs. For the latter I am almost tempted to use the word ‘reefery’; 
for the former I have, in this passage, used the expression ‘individual coral 
reef’), or rise on one side from great depths, having on the other comparatively 
shallow water, have generally a linear form, being three, five, or ten miles 
long, and varying in breadth from one or two hundred yards to perhaps a mile. 
This seems to be more especially the case when their direction runs across that 
of the prevailing wind. The individual coral reefs which rise from an equal 
1 Ueber den Bau der Korallenriffe und die Planktonvertheilung an den Samoa- 
nischen Küsten, von Dr. Augustin Krämer, Kiel, 1897, p. 65. On the preceding page 
Krümer has figured the reef flats to the eastward of the entrance of Apia covered 
with coral débris which resemble the uninteresting reef flats of the Great Barrier 
Reef, and which I had an opportunity of examining when at Apia. See also 
A. Agassiz, The Coral Reefs of the Hawaiian Islands, Plates VIII., IX., Bull. 
M. C. Z., Vol. XVII. No. 3, 1889. 
