THE AUSTRALIAN GREAT BARRIER REEF. 107 



on the edge of the reef, and wade ashore a distance of a third of a mile. The bottom was very 

 irregularh', but pretty equally, divided between white sand and blocks of dead and living coral, 

 principally the former. On many of the rough blocks of coral there was scarcely a few inches of 

 water, and many large masses, particularly along the outer edge of the reef, were high and dry. 

 All the sandy spots, however, were about three or four feet deep, and as neither the sandy spots nor 

 the coral-masses were anywhere continuous for more than a yard or two, we had a succession of 

 wading and scrambling that was rather laborious. Arrived at the island, the first thing that took 

 my attention was a large development of hard brown rock, like that on Bunker's Island. Both the 

 island and the reef were elongated in an east and west direction, the island being half a mile long, 

 and not more than 300 yards broad. It consisted in the interior of piles of loose sand, covered by 

 a dense wood of pretty large trees, with broadish leaves, most of which had a white brittle wood, 

 and grew in a singularly slanting position, the stems frequently curving at an angle of 45°, although 

 three or four feet in circumference. The beach of the island was steep, about twenty feet high at 

 low water, and composed partly of sand and partly of stone. The sand was very^ coarse, composed 

 wholly of large grains and small angular pieces of comminuted corals and shells, with some larger 

 worn fragments of both intermixed. The stone was of precisely the same materials, but very 

 hard, and dark brown externally, although still white inside. It sometimes required two or three 

 sharp blows with the hammer to break even a corner of it off. Its surface was everywhere rough, 

 honeycombed and uneven ; the beds from one to two feet in thickness, with, occasionally, in the 

 fine-grained parts, a tendency to split into slabs or flags. It was perfectly jointed by rather zig- 

 zag points crossing each other at right angles, and splitting the rock into quadrangular blocks of 

 from one to two feet in the side. As far as external appearance and character went, it might have 

 been taken for any old roughly stratified rock. As to position, the strike of the rock was parallel 

 to the direction of the long diameter of the island and reef or east and west ; and it dipped on the 

 north and south sides of the island to the north and south respectively ; or from the island towards 

 the reef at an angle of 8° or 10°. At the east end of the island it was not visible, but at the west 

 it appeared from under the sand in two places, in one being horizontal, and in the other having a 

 slight flexure or anticlinal line, which ranged also east and west. The rock was in man}' places 

 much worn by the wash of the breakers, which had also a good deal undermined it in some places, 

 and many blocks had fallen down in a line. The joints were parallel to the dip and strike 

 respectively. The rise and fall of tide here was fourteen or fifteen feet, and at high water the 

 upper part of the rock was just about covered ; at low water the reef was dry for a small space all 

 round the island. Now the question is how or under what circumstances did the loose calcareous 

 sand and fragments become hardened into solid stone, acquire a regular bedding and a jointed 

 structure, and the plane ol stratification assume an inclination of 8° or 10°. If it be supposed that 

 a regular deposition and slope of 8° took place every high tide, and a gradual and successive in- 

 duration went on, why does not the same thing take place now ? or why did not the loose sand 



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