76 The Geology of the Portland Promnontory, 



That these cliffs were somewhere breached so as to admit 

 the sea over the lower land behind them, and thus an 

 inland sea was created, resembling, in the form of its sea 

 wall, Port Phillip Bay, Port Jackson, or the Gippsland 

 Lakes. In the quiet waters of such a closed-in sea, the 

 undulating surfaces of the limestone hills, with their shelly 

 investiture, might have been preserved intact. Similar 

 shaped banks now occur in Port Phillip Bay, especially 

 towards the Heads, and they are known to be similarly 

 covered with shells. The slowly retreating waters of Port 

 Phillip BajT- are to-day leaving behind them, all round its 

 shores, shell beds in nowise different in appearance from 

 those on the hills and cliffs of Nelson and Bridgewater. 

 These shell beds are intermediate in age between the 

 pleistocene limestone and the recent dunes. 



VIII. — Maeine Beds, Bolwaera. 



Between Portland and Narrawong the cliffs recede inland. 

 Alluvial flats, crossed by low sand ridges, take the place of 

 the bold hills of lava and limestone. A very old resident 

 of Portland, Mr. Douglass, to whom I am considerably 

 indebted for local information, tells me that a farmer living 

 on these flats has bored for water. The rod passed through 

 many beds of drift sand, mud, and clay, and reached a depth 

 of 100 feet without meeting with any indication of a bed- 

 rock. From the nature of these beds, I judge that the 

 locality was once the site of an arm of the sea, and the 

 present contour of the land suggests that, in the immediate 

 past, a narrow strait cut off the bold extremity of the 

 Portland promontory from the main land, leaving it a small, 

 steep-sided, volcanic island. 



IX. — The Raised Beaches and the Sea Caves. 



AU along this coast there is evidence of much recent 

 change in the sea level. On the Portland beach, in front of 

 the Court House, the chalk cliffs are undercut, showing that 

 the waves once reached them. The entire cliff face is 

 vertical, and is so sharply cut and so slightly weathered, 

 that much time cannot have elapsed since this happened ; 

 but the grass-grown sand heaps at their bases indicate that 

 the sea has retreated. 



