BY DR. W. N. BENSON. 35 



lower portions, but the gorges had not cut back to the 

 heads of the streams. During this period of alternating 

 uplift and aggradation, flows of basalt occurred on several 

 occasions outside the special area here considered. The 

 oldest basalts, with their intercalated gravels, cover Mid- 

 -cijesex Plains, and were probably connected with those 

 above Lorinna on the other side of the Forth Gorge (as 

 shown by Mr. Twelvetrees). The upper portion of the 

 gorge is a wide, open valley, in which there is a thick mass 

 of gi'avel covered with basalt. Below this there are 

 newer gravel terraces, and the present stream has cut down 

 below these, thus giving a perfect example of a valley-in- 

 valley topography. (See Bibliography 42, Plate IV.) 

 According to Mr. Andrews's view, the gravels were pro- 

 bably deposited during periods of subsidence between the 

 successive uplifts, (i^). 



The remaining periods are those of maximum glaciar 

 tion, retreat of the glaciei^, and finally the period of 

 f.ost-glacial erosion. Possibly further research will show 

 that the period of maximtim glaciation comprised two or 

 more maxima with intervening periods of retreat, as has 

 been determined for the glaciation on the mainland, (^^) 

 but there is not sufficient evidence to permit of this con- 

 clusion at present. The period must here be considered as 

 ■a, whole. 



Glacial features have been noted in this region by 

 Sprent (3), Montgomery (9, 13), Waller (21), Twelvetrees 

 (31), and Nostling (38), but no detailed description has 

 been given. At the time of maximum glaciation an ice- 

 sheet extended over the whole region, the three main pro- 

 iTiinences being probably the only points emerging above 

 the snow. The main directions of ice-flow were deter- 

 mined by the pre-glacial valleys that were roughly radial 

 about Cradle Mt., but important over^^ow-glaciers were 

 developed as the level of the ice rose, and adjacent streams 

 became confluent. In describing the manner in which 

 these influenced the topography, we commence at Barn 

 Bluff. The ice moved radially from this peak. To the 

 west it fell over the gorge of the Fury, and was 

 there broken up and melted. It does not seem likely 

 tnat any mass of ice moved down this valley, since it ap- 

 pears to be a typical water-worn valley with overlapping 

 spurs. To the south-east the ice moved out on to the 

 plateau, scooping out the broad and probably shallow 



(12) E. C. Andrews. G^eograpliical Unity of Eastern Australia. 

 Joum. and Proc. Roy. Soc. N.S.W., pp. 420-480, especially p. 455. 



(13) David, Helms, and Pittman. Proc, Linn. Soc. N.S.W,, 1901, pp. 

 26-74. David. Ibid., 1S09, pp. 657-668. 



