AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA, 119 
dead elevated coral reef, which forms the core of the reefs on the dead 
summit of the reef flats left awash. Тһе slopes of the reef flats are 
generally very gradual from the edge of the reef left awash at low tide 
to the clean sand slope found beyond the point at which corals and heads 
begin to grow. Where the water is deeper than ten fathoms off the reef 
flat faces, the slopes are usually somewhat steeper, the coral patches and 
heads rising more vertically from their first appearance, and thus seeming 
to grow upon a steeper slope. 
Our next anchorage was south of the Lark Passage (Plate ХХХІП.), 
on the inside of the outer line of breakers in twenty fathoms, about an 
eighth of a mile from the narrow reef which forms the southern are of 
breakers bounding the Lark Passage. As far as the eye could see, the 
outer reef formed a series of these arcs slightly overlapping, the shape of 
which was clearly indicated by the line of huge breakers pounding upon 
the narrow flat belt of dead corals which separated the outer edge of the 
reef from the interior passage in which we anchored. ‘This part of the 
exterior edge of the Great Barrier Reef differs in no way from the inner 
reef flats we have already examined, As we approach it from the west 
the coral patches and heads make their appearance in from seven to six 
fathoms. At first widely separated, then in from five to four fathoms 
they become more closely connected, and finally form a nearly continuous 
belt incrusting the inner reef slopes. The growth of coral becomes less 
and less again as we pass into shallower water, and when we reach the 
reef flats with two to three feet of water upon it, the corals have become 
reduced to a few small and scattered heads, the greater part of the 
reef flat being covered with dead corals and fragments of dead corals 
upon which Alge and Nullipores flourish. The width of the reef flat, 
between the inner line of breakers and the inner edge of the reef 
flat slope, varied from 200 feet to about 800 feet. Unfortunately, 
the state of the sea on the outside of the reef was such that it was 
impossible to examine the condition of the corals growing upon the 
sea face of this outer reef flat." From what I have been told by 
1 Kent states thirty fathoms to be the limit at which reef corals grow. He must 
refer to observations beyond the area of the Great Barrier Reef, as he does not 
state that he has taken soundings to ascertain their lower limit. As far as my own 
observations are concerned, they are limited to the bathymetrical range of the reef 
corals on the slopes of inside reefs, or on the lee of the outer line of reefs, and 
nowhere have I found them, as stated elsewhere in this paper, to reach the limit 
assigned to them by Kent. Iam unable to understand the assertion so frequently 
made and repeated by Kent and Krämer that the lee faces of a reef show by far the 
greatest development of living corals. The growth,of the reef corals is so fre- 
