During Post-Miocene Times. 17 



merged by the ocean rise, was an island, shaped like a jack- 

 boot, with the Darling Downs for its uppers, the Howe for 

 its heel, the Grampians for its toe, and the Adelaide ranges 

 for its Sicily; while its long rocky length lay north and 

 south, right athwart the course of the chilly, moisture- 

 bearing winds. 



In the other hemisphere the edge of permanent ice moved 

 down from 77° N. to 50° N., or an advance of 27 clegs. If 

 a similar advance was made in this hemisphere the ice 

 barrier must have been in 43° S., which is the latitude of 

 Hobart. Nor is there anything extraordinary in this 

 supposition, for New Zealand has even now, in the same 

 latitude, a glacier which descends within 700 feet of the sea ; 

 while South America has, in 46° S., glaciers which dip into 

 the sea and shed icebergs. If, therefore, the ice-barrier 

 were then as near to us as 43° S., our coast would have been 

 cumbered with bergs and floes, and the mountainous island 

 of Australia must have been as cloaked with ice and snow 

 as the Georgias are to-day. Australia might not be high 

 and large enough to nourish a true continental ice-sheet, but 

 every range would have its confluent glaciers, whose pro- 

 jecting feet might plough up the shallow foreshore. 



According to Croll's calculations there must have been a 

 lowering of the temperature, which would vary between 

 29.5° S. and 37.7 E. (C. and T., p. 316). The present mean 

 temperature of Victoria is 58° F. If we take this as a 

 standard, and deduct the lower amount, the result will give 

 us 3° below freezing point as the mean temperature of Vic- 

 toria during the glacial epoch ; and if we make our mean 

 winter temperature, which is 49°, our standard, then the 

 temperature would have a mean of 12° below the freezing 

 point, and that of Sydney would be about 7° below — that is 

 to say, the temperature would be that of South Greenland in 

 winter time. We must not forget that at this time there 

 was a lofty sandstone plateau of miocene age where our 

 Dividing Range now stands, and that these highlands probably 

 had an altitude of at least 2000 feet greater than the present 

 peaks. The glaciers these extensive chilly heights would 

 breed may have been the main factors in filing down their 

 even crowns into the existing series of sierras (Howitt, 

 R. S. T., Vol. XVI.). The debris of these peaks may have 

 supplied the material to build up the sandstone plateaux of 

 Central Australia, whose flat surface of cretaceous age was 

 in those times submerged, and which, it is probable, was 



c 



