AGASSIZ: THE GREAT BARRIER REEF OF AUSTRALIA. 101 
The outer edge of this portion of the reef is formed by a series of linear 
or curved reefs of but little width, separated by deep and narrow chan- 
nels, against which thunders the incessant Pacific swell. The inner edge 
of this line of reef patches is separated from the irregularly shaped reef 
patches which constitute the width of the reef by deep tongues of 
water, forming a more or less irregular deep continuous navigable 
channel of from ten to twenty fathoms, or even more, and of very vari- 
able width. Off Cape Bedford to the north of Lark Reef the reef 
patches become more distant and distinct, and as far north as Direction 
Island they are often widely separated. The reef flats of the inner part 
of the reef between Lark Reef and Aitch (h) Reef especially are widely 
separated, leaving an almost uninterrupted passage from Lark Reef to 
Lark Passage on the south, and similar passages to the north leading to 
the interior channel immediately to the eastward of the cluster of reef 
patches lying east of Aitch Reef and the Lizards and the narrow outer 
line of disconnected exterior reef patches extending from Lark Opening 
to One-and-Half-Mile Opening. 
This outer interior channel north of Lark Opening varies in depth 
from ten to fifteen fathoms. East of North Direction Island it opens 
out into a broad bay from ten to twelve miles wide, reaching round the 
Lizards to north of the Turtle Islands, the narrow line of linear reefs 
forming its eastern boundary. North of One-and-Half-Mile Opening the 
reof patches within the outer line of reefs again constitute a belt varying 
from ten to twelve miles in width. We did not extend our examination 
beyond the line of the Lizard Islands and Eagle and Em (m) Reefs. 
Both these reefs are within the ten fathom line. 
South of Cape Flattery (Plates XXXIII., XXXIV.) the Low-wooded 
Isle, Three Isles, and Two Isles are the only remnants of the numerous 
but somewhat widely separated islands which once existed between that 
cape and the outer edge of the Barrier Reef, the others having been eroded 
and changed to the reef flats and patches now existing to the eastward of 
these islands. Going north we come upon the Rocky Islets, South and 
North Direction Islands, and the Lizard group, the last of which occupies 
a considerable area and rises to a height of nearly 1,200 feet. The 
windward faces of all these islands and the flats surrounding them are 
flanked by coral, growing on their slopes and rising from a depth of from 
seven to ten fathoms. 
To the north of the Lizards the outer edge of the Barrier Reef trends 
more to the westward, running parallel to the coast of the mainland to 
off Cape Melville, where it is not more than twelve miles from the coast, 
