228 Notes on Post Tertiary Strata 



their gradual consolidation is producing a similar rock. 

 Thus, at Swan Lake, in the very heart of the drifting sand 

 hummocks, the rock crops out where the overlying sand of a 

 partially consolidated dune has been blown away by the 

 wind, the exposed hardened portions showing the quaqua- 

 versal dip that is so striking in the Nelson Bay cliffs. 

 Indeed, on the very margin of this small lake, minor cliffs 

 have been formed, which are miniature copies of those 

 against which the foaming waves of the Southern Ocean 

 dash themselves. Occasional outcrops of the rock may, in 

 fact, be found in almost any part of the hummock region 

 from Portland Bay to the boundary of the colony. At the 

 Glenelg mouth it is seen in different stages of formation, 

 from solid rock down to that which is so loose and crumbling 

 as to give way at the slightest touch. 



With the aid of a lens the component parts of the rock 

 can be fairly well distinguished. Little white specks, which 

 run pretty evenly through it, are simply small pieces of 

 shells, usually thin and sharp; but the main mass consists of 

 rounded fragments of corals, bryozoa, &c. It is true that 

 whole shells are sometimes found among the recent hum- 

 mocks, and their absence from the rock might at first sight 

 seem strange ; but it must be remembered that the sand is 

 in continual motion, being drifted hither and thither by the 

 force of the wind, and long before consolidation could take 

 place they would be broken into unrecognisable fragments. 

 At Bridgewater and other places where the sand is still 

 unconsolidated, recent shells are found, not only in hollows, 

 but also for a considerable distance up the dunes. It is not 

 difficult, however, to understand how they came there, 

 since shells are at the present day being deposited on the 

 shifting sand dunes of the beach in precisely the same 

 manner, washed up, no doubt, by the surf during storms. 

 It is evident that these mounds of loose sand can never 

 have been submerged after being once formed, or they would 

 speedily have been levelled by the waves. 



The same remark may, of course, be made with regard to 

 the inland dunes, while they were yet in the unconsolidated 

 state; and it is probable that a gradual elevation of the 

 coast-line has continued during the formation of the entire 

 series of dunes. 



There are two minor deposits on the coast which may be 

 mentioned here. At Narrawong, and also near the mouth 

 of the Glenelg, on the landward side of the coast hummocks, 



