98 bulletin: museum of compaeative zoology. 



ing small islands on the south. The 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 feet, 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 Eeef. 

 The 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 ofcthe Barrier Reef. Penrith Island 

 itself is flanked by a small coral reef fiat. To the westward of Whitsunday 

 Passage the coast shows but few traces of erosion, Gloucester Island and 

 Magnetic Island being the only two islands of any size occurring in a 

 stretch of about 120 miles, until we reach the Palm Islands (Plate 

 XXX a .). 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 been separated 

 from it, as have Gloucester and Magnetic Islands. 



Off Hook Island, the inner edge of the Great Barrier Reef patches is 

 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 sea-face slopes gradually 

 from the outer line of patches from ten to forty-five lathoms 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, 



