24 T. S. Hall: 



rock fi>riiis the surface, and the typical form of the cups so 

 characteristic of dunes is easily traced. In other places we find 

 lon<r, branching and anastomosing ridges, the dune-rock being 

 frequently capped by the white so-called travertine, the residue 

 of evaporated ground water. 



We thus have two limestones, the lower one a marine, poly- 

 zoal-rock, and the upper an aeolian one. Ttie marine limestone 

 affords a richer soil, and aJt the same time flints are commonly 

 scattered on the surface, while they are not found in the dune- 

 rock. So that the presence of flints is a key to the underlying 

 rock. 



It will be seen that a large number of the low ridges aaid hills 

 eanmit be ascribed to subterranean denudation, for in the flats 

 and valleys between them flints often occur, and swallow holes 

 and caves are common. The hills are isolated, or practically 

 isolated ridges of cadcareous, wind-borne sand. It is essential 

 that this fact be insisted on, and I paid attention to it in several 

 places in the district. The dunes extend inland for many miles, 

 and probably lose their marine origin as they pass north through 

 the mallee country. 



A mile to the south of the town of Mount Gambler occurs the 

 mount itself, a volcanic pile. There has been practically no 

 effusion of lava. A sheet of it is seen inside the shattered crater 

 walls, and was the first material ejected. The tuft's extend for 

 two or three miles round the foot of the mount, and are of no 

 great thickness. 



A little more than a mile south of the mount is a long east 

 and west ridge of dune rock. This rises some fifty feet above 

 the surrounding country, and is crossed by two roads, one going 

 south to Port Macdonnell, and the other a couple miles east 

 of it, leading to Nelson at the mouth of the Glenelg river. Both 

 these roads pass through cuttings about twelve feet deep and 

 show dune rock capped by tuffs. The tuffs are well-bedded, 

 quite as distinctly and as evenly as anything shown about 

 Camperdown. They, moreover, show a marked peculiarity in 

 that they follow the contour of the ground closely. It is not a 

 case of a tuff' capping the hill and being missing on the flanks. 

 The bedding planes are parallel to the present surface. They 

 rise from the north, cross the rid<re and sink down towards the 



