

During Post-Miocene Times. 7 



Promontory. The Rev. W. B. Clark reports ice markings 

 on the mountains of New South Wales, and the Rev. 

 Julian Woods, in his Geological Observations in South 

 Australia, writes (p. 20) that " it seemed to him that 

 there were very distinct marks of snow and action of 

 glaciers" on the flanks of Mount Lofty, near Adelaide. 

 Mr. Gavin Scoullar read a paper some time since before the 

 Adelaide Philosophical Society, in which he describes a 

 boulder drift at Hullett's Cave which rests upon a well- 

 striated pavement of rock (P. 3. T., 1877-79, p. 65). 



Professor Tait, in an address to the same society, describes 

 smooth, striated, grooved rocks in the bed of the Inman, 

 Cape Jarvis (id., Vol. LXV.). Selwyn had seen these last- 

 named rocks long before, and he tells us that " the direction 

 of the grooves and scratches is east and west, in parallel 

 lines," and he adds — " I do not think they could have been 

 produced by the action of water. They strongly reminded 

 me of the similar markings I had so frequently seen in the 

 mountains of North Wales" (Selwyn's Notes on South 

 Australia, p. 4). 



Professor Tait also describes smoothed, grooved, striated 

 rock surfaces, and morainic debris of angular blocks of red 

 granite, gneiss, hornblende, and quartz, at Black Point, 

 Holdfast Bay ; and he points out the circumstance that the 

 nearest source from which these rocks could have been 

 obtained is thirty -five miles distant. All these South Aus- 

 tralian indications of ice are said to be of pliocene age (id., 

 Vol. LXIV.). 



I am not aware of the occurrence of any other examples 

 of rock striae, within South-eastern Australia, of post-tertiary 

 date. There are others to be found, as those of the Leder- 

 derg, but they are believed to be of miocene age. 



The scarcity of such evidence is accounted for easily in 

 several ways. For instance, rocks differ in their capacity to 

 retain markings. Limestone, serpentine, and clay ironstones 

 polish well, and preserve their striae long, while sandstones 

 streak faintly and weather quickly. All the softer rocks, 

 and those which are highly jointed, break up rather than 

 polish (Great Ice Age, pp. 16-21). Further, those which 

 are impregnated with salts decay quickly. Now, our 

 silurian slates, sandstones, and shales are loaded with iron 

 oxides, and are upedged; while our recent marine sandstones 

 abound in the chlorides of magnesia and soda. Therefore 

 our rocks are to a large extent ill-suited either to receive or 



