HOUTMAN ABROLHOS ISLANDS. 155 



reef-flat. The cliffs themselves rise to a height of 30 feet, and the greatest 

 elevation, only a little distance inland from these, is upwards of 50 feet. 



This south-western corner of West Wallaby Island presents the finest 

 scenic picture of the Abrolhos Islands, the cliffs are of rugged weathered 

 limestone, and the margin of the outer reef swings in at this place until it 

 comes quite close to the extreme S.W. point. The full swell of the ocean 

 breaks, therefore, quite close to the island, and the waves rush across the reef- 

 flat wearing deep pot-holes and excavating the coast. The photographs 

 illustrate the type of coast at this point (PI. 14. fig. 7). 



It is very interesting to note that the mile of coast on the south-western 

 shore of the island should resemble closely the stretch on the north-east of 

 East Wallaby Island. Everywhere else on the Wallaby Islands the margin 

 is much lower and with either sand or low-lying limestone. 



Another point of great interest on the West Wallaby Island is the 

 occurrence of a well-marked terrace on the western cliffs, about 6—8 feet 

 above the level of the reef-flat. A similar terrace, slightly lower in places, 

 is found, as already stated, on the N.E. shore of East Wallaby Island. We 

 shall see later that there is evidence on the Abrolhos Islands of a recent 

 uplift of 8 feet or so. The terrace represents the old sea-level before 

 the last elevation. 



A considerable part of the area of the West Wallaby Island is low-lying, 

 being about 6 feet above sea-level. This applies to all the north-eastern 

 portion (about a square mile) and the southern part of the East coast. The 

 north-eastern region presents a surface which is largely flat limestone — 

 resembling in appearance that photographed by Fryer on Picard Island 

 in the Indian Ocean and described as " platin." It is covered with the usual 

 stunted halophytic bush. In most places the limestone is completely hidden 

 by a layer of guano and sand which looks as if inhabited by thousands 

 of rabbits. The excavations are, however, due to mutton-birds, and as they 

 are not very deep it is usual for anyone trying to walk over this area to fall 

 through with oae foot or both at every other step ! The pavement-like 

 surface of the limestone has been probably produced by successive solutions 

 and redepositions of calcium carbonate by rain-water — the guano aiding. 

 In past times a large quantity of guano was removed from West Wallaby 

 Island and the ruins of an old cam]) and about 1£ miles of tramway 

 still exist as relics, whilst a wooden pier runs out for a considerable distance 

 on the west coast into the waters of the lagoon. 



We devoted some little attention to the limestone exposed on West 

 Wallaby Island, especially on the West coast where there was a thickness 

 of 25-30 feet above sea-level. The lowest parts at this place consist of a 

 compact rock, granular in appearance, fairly hard and without any traces of 

 corals or molluscs. Microscopic examinations, kindly carried out for me 

 by Professor Woolnough, of the University of West Australia, reveal the 



