i8o Excursion to National Park. [y^J^ 



Vict. Nat. 

 XXIX. 



quartz-grain-bearing limestone to almost pure limestone below. 

 This is due to the action of the carbonic acid in the rain falling 

 on the dunes acting as a solvent of the calcareous shell frag- 

 ments contained in the upper layers. Where the dunes have 

 been piled up on the granite, as at the south side of the mouth 

 of the Darby River, and where the slope of the granite surface 

 is towards the sea, there may be seen, on exposed portions of 

 the granite, a coating greatly resembhng " boiler scale." In 

 this case the percolating rain water, containing hme from the 

 top layers, soaked down till it met the im^^ervious granite. 

 It then drained along the rock till it emerged at the lower edge 

 of the dune, when, the water quickly evaporating, the lime 

 was re-deposited in thin layers, as normal calcium carbonate, 

 on the rock surface hke a coating of cement. 



Lying in the encircling arms of the eastern spurs of the 

 Vereker Range is an interesting stretch of grass-tree-covered 

 high plain — ^the Bull Plains. Looking at it from below — 

 anywhere along the lower part of Barry's Creek — it presents 

 the appearance of a huge grass-covered earthen embankment 

 of some reservoir. Closer examination suggests that it is the 

 remains of a small flatfish hill which has been denuded without 

 stream dissection ; but, as the head-waters of Barry's Creek 

 are now working round it between the encircling hills, in the 

 course of time it will become what may be termed an " island 

 plateau." 



There seems no doubt that at some period of its history the 

 Promontory was an island, with a stretch of shallow water 

 between it and the mainland. At Yanakie, some little 

 distance north of the dividing fence, there is a contact between 

 the granite and the Silurian which shows the former to be 

 the younger. Westerly and south-westerly winds seem to be 

 the prevailing weather. The sea has banked up the sand on 

 the submerged neck till it emerged from the water on the 

 western side. Since then the dune formation has raised the 

 level of the land, and is gradually pouring sand into the water 

 on the western side of Corner Basin, which at the j^resent time 

 is a shallow stretch of water with, in most jmrts, a muddy 

 bottom. Though there is a fair range of tide, there is prac- 

 tically no scour except in the neighbourhood of the eastern 

 entrance. The sand that is blown in from the western dunes, 

 and the mud and silt brought down by the mainland streams 

 and those flowing north on the Promontory, are slowly but 

 surely filling up the Basin, and it seems as if in a short time, 

 geologically speaking, Corner Basin will be non-existent, and 

 Doughboy and the other islands will ]:)ecome merely granite 

 outliers surrounded by plain and sand-dune country. 



