98 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
ing small islands on the south. Тһе summits of many of the islands 
reach considerable heights. Hook and Whitsunday Islands are over 
1,400 feet in height ; one of the smaller islands, St. Bees, is over 1,200 
feet, Shaw Island is more than 1,300 fect, and many of the lesser islands 
rise to heights between 500 and 900 feet. 
The islands to the east of Whitsunday Passage rise from the ridge within 
the twenty fathom line, as those of the Cumberland Islands on the same 
side of the Hillsborough Channel rise from the ridge within the ten and 
the twenty fathom lines (Plate XXX.). The inner edge of the Barrier 
Reef is about twenty miles from Penrith Island, and perhaps thirty from 
Whitsunday Island. Its depth is most irregular,— within the limits of 
the twenty fathom line on the west, and twenty-five to thirty fathoms 
close to the line of the reef patches on the inner edge of the Barrier Reef. 
Тһе soundings in the channels within the reef patches gradually deepen 
towards the outer edge of the Barrier Reef from twenty to thirty-five or 
thirty-six fathoms. In this part of the inner Barrier Channel there are 
only a few small reef patches to the east of Penrith Island, which are the 
westward extension of the inner limits of the Barrier Reef. Penrith Island 
itself is flanked by a small coral reef flat. To the westward of Whitsunday 
Passage the coast shows but few traces of erosion, Gloucester Island and 
Magnetie Island being the only two islands of any size occurring in à 
stretch of about 120 miles, until we reach the Palm Islands (Plate 
XXX). Edgecombe, Abbot, Upstart, Bowling Green, Cleveland, and 
Halifax Bays are deep indentations, the eastern promontories of which 
are still connected with the mainland, and have not as yet boon separated 
from it, as have Gloucester and Magnetic Islands. 
Off Hook Island, the inner edge of the Great Barrier Reef patches i8 
less than twenty miles distant, and their width about thirty miles. On 
the inner edge off Hook Reef, the depth of the inner channel varies from 
twenty-four to thirty-four fathoms, and the sca-face slopes gradually 
from the outer line of patches from ten to forty-five fathoms towards the 
100 fathom line, distant about ten miles. At the inner entrance to 
Flinders Passage the depth is about twenty-five fathoms, the distance 
from Cape Upstart being twenty-five miles, where we find ten fathoms 
close inland, and the fall gradual from there to the outer entrance of 
Flinders Passage, thirty-seven fathoms, at a distance of about sixty 
miles, 
The reef is not more than twenty-five miles wide between the north 
side of Flinders Passage and the northern side of Palm Passage, the 
outer entrance of which is about fifty miles from the Palm Islands, 
