Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/394

 not the high land is central, as usually occurs. This well-marked margin is most developed along the west and east coasts, where the hills form a lofty continuous chain. The former runs at a distance of from 200 to 300 miles and upwards from the coast, and sometimes attains an altitude of more than 4000 feet above the sea-level. Its fellow, longer, loftier, and so pronounced as to form a well-marked back-bone to Eastern Australia, stretches from Cape Howe to Cape York, lying from 10 to 20 or 50 miles inland, and culminating in the Bellenden-Ker hills (5158 ft.) at the base of the Cape- York peninsula, but thence onward gradually decreasing in height, till close to Torres Strait they are seldom more than 300 feet above the sea- level.

The Cape- York peninsula now alluded to, triangular in shape, is about 300 miles wide at its base, with a length thence northward to Cape York of more than 400 miles. Its mountain-range, a continuation of that further south, runs up along its eastern border, decreasing in height pari passu with the diminishing area of the land. On its east coast and within five miles of Cape York lies Albany island (see Map), three miles long, on an average half a mile broad, and separated from the mainland by the Albany Pass, a narrow gorge from 7 to 14 fathoms deep, and from half to three-quarters of a mile broad, through which the tide rushes with great force either way. Historically interesting from the fact that it was once the intended site of Somerset, but wisely abandoned, on the recommendation of the present Hydographer to the Admiralty, for a more eligible bay on the mainland opposite, Albany island is geologically interesting from the circumstance that it forms the principal centre from which we now take our survey of this part of Australia.

The range which thus forms a marked feature in the physical geography of the Cape- York peninsula, consists, as it does further south, of an axis of volcanic rock of varying constitution, but chiefly granite, porphyry, gneiss, felspar, and quartz. Thus the vicinity of Port Denison, Cape Melville, and the coast about Cape Direction, and Weymouth and Fair Capes are granitic, and the pointed end of the peninsula porphyritic, while some of the offlying islands, outliers, so to speak, of the main range, likewise differ : e. g. Dunk Island, the Family group. Lizard Island, the Forbes and Hardy Islands are aU granitic, the Franklands gneissic, and Sunday Island flesh-coloured compact felspar. The islands of Torres Strait may be regarded as an interrupted portion of this range, which is doubtless continued into New Guinea. Of these. Turtleback, Mount-Ernest, Poll, Banks, Burke, Mount- Adolphus, and the Farewell Islands are all granitic. Towards Cape York this igneous axis has undergone less elevation ; still the underlying crystalline rock occasionally appears above the surface as intruded masses of porphyry, surrounded and overlain by more recent formations. For example, at the north end of Albany Island it forms a large boss ; at Osnaburg, Bishop, Ida, and Evans Points, and at Cape York we find it in bluffs and promontories ; and at Ida, York, and Eborac Islands &c., in more elevated masses or isolated hills which culminate in