During Post-Miocene Times. 9 



as scoop out, these rock basins, and that they often leave 

 finally a plain of deep alluvium to replace a rocky floor 

 removed. Lake basins thus obliterated are hard to identify, 

 and may be overlooked easily. Some such levelled-up moun- 

 tain tarns are known to exist here. Mr. J. Stirling has 

 recently described one in a paper contributed to this Society 

 entitled the " Physical Features of the Australian Alps." In 

 it he writes thus : — " Occupying the valley of the Living- 

 stone Creek since the lower silurian rocks became metamor- 

 phosed into the present crystalline schists were a series of 

 ancient lakes or tarns, into which, by the breaking up of the 

 ancient lava flows, masses of igneous boulders became 

 deposited. Subsequently the gradual wearing down of the 

 metamorphic schists, with their associated auriferous quartz 

 veins, fiiled up these ancient lake beds with a deposit of 

 boulders and auriferous gravels. Ultimately the Livingstone 

 Creek . . . eroded a channel along its margin, leaving 

 the deposited gravels, with their underlying false bottom of 

 igneous boulders, literally high and dry above the bed of the 

 latter stream" (R. S. T., 1882, p. 106). Now, there can be 

 but little doubt that it was the glacier which scooped out 

 this lakelet, and also broke up the debris with which it is 

 filled. As the ice melted a watery flood swept down the 

 glacier rubbish from above, and levelled it to the brim. 

 Then the surplus debris passed on to fill up other pools lower 

 down.' The mountain creek which succeeded to the glacier 

 eventually cut through the formation and revealed the story. 



Brough Smyth records that there are amongst the Gipps- 

 land hills many level tracts of alluvium, from 200 to 300 

 acres in extent, surrounded by precipitous rocks and situated 

 at the junction of streams. I think that these will eventually 

 prove to be similar filled-up tarns of glacial origin (B. 

 Smyth's Goldfields, p. 12). 



In the watershed of the Ovens there are hollows in the 

 granite, now filled up with sedimentary strata, which may 

 also be numbered amongst the traces of ice erosion in Vic- 

 toria (B. Smyth's Goldfields, p. 83). 



If we step down from the mountains we shall see that 

 our miners have discovered, beneath the smooth wide plains 

 and the softly swelling rises which diversify them, an 

 ancient land surface of very different contour. This con- 

 cealed earth -surface is composed of bare silurian rock, which 

 has been sculptured by natural agents until it is ribbed and 

 guttered like the fluted face of an old clay cutting, but with 



