154 GEOLOGY OF QUEENSLAND COAST, 



Gloucester Island rises abruptly from the sea to a height of 

 2,000 feet, and from a short distance much resembles a giant 

 headland, so narrow is the channel between it and the Queensland 

 shore. 



Magnetic Island, 1,600 feet in height, is roughly rectangular 

 in plan, and composed of a dark granite admirably adapted for 

 building purposes. Unlike the granite of the Towns ville foreshores 

 (five miles distant) and Castle Hill, it is homogeneous in character, 

 and iDossesses cuboidal jointing. This island is further interesting 

 by reason of certain rock-markings which point to recent eleva- 

 tion. Mr. G. Butler, of Towns ville, mentions the presence of 

 masses of oyster shells at a height of from 10 to 15 feet above 

 H W.M., and removed some 50 feet from the sea. These shells, 

 he says, are attached to the solid granite composing the island, 

 and not to loose boulders. Maitland, also, from a discover}' of 

 pumice fragments some distance from the present sea level, claims 

 recent elevation for this island."^ 



The Palm Islands. — This cluster was examined in some slight 

 detail, and was found to consist of granites of varying acidity 

 and quartz-porphyry, traversed by regular networks of basalt 

 dykes. 



Generally speaking, they are rugged and barren in character, 

 and, with the exception of a few sandy bays, possess precipitous 

 and rocky coasts. Large black rounded granite tors cover the 

 hill sides. 



South Palm is 7 miles in length and about 3 in width. It 

 consists of two peaks 1,400 and 1,820 feet respectively in height. 

 The rock of the island is an ordinary ternary granite, with a 

 tendency, however, to pass into acid types by reason of a diminu- 

 tion in the quantity of biotite. Large segregations of quartz and 

 pink orthoclase may be seen in the granite outcrops. Masses of 

 orthoclase occur as much as 1 2 to 1 5 inches in diameter, as also 

 quartz. On the north-east of the island a remarkable floor or 



* Maitland, Kept. Magnetic Island. Brisbane, bv authority, 1892. 



