Glaciation in the Australian Alps. 31 



flowing under some parts of a glacier, and much melting 

 and relegation of ice aje going on in different places, stones 

 are liable to change their position, in which case a second 

 set of striae and furrows niay be imprinted in a new direc- 

 tion. In like manner, the solid rock underneath the glacier 

 may exhibit scratches and grooves in more than one direc- 

 tion; the furrows will, most of them, coincide with the 

 general course of the valley; but as the ice in different 

 seasons varies in quantity the direction of its motion at a 

 given time is not uniform, so that the grooves and scratches 

 will also vary, one set often intersecting another."* Again, 

 it may be said that the samples of mica schist present only 

 weathered parts along cleavage lines and at softer spots ; 

 but this objection may be met by stating that the groovings 

 are found exactly in that position where the grinding and 

 gouging power of glacial debris under the ice sheet would 

 be most likely to prove effective, and that the groovings are 

 persistent across the cleavage lines as well; and further, 

 that no similar markings are found on similar rock masses in 

 other parts of the valley, although exposed to the degrading 

 influences of atmospheric agencies. 



The rounded outlines of the gneissic and other metamor- 

 phic rock masses on the hill-sides may also be attributed to 

 mere weathering ; but the striations on these outcrops which 

 cross the bedding planes and cleavage lines seem to offer 

 indisputable evidences of glacial abrasion. They occur also 

 at what was probably the mean height of the latest valley 

 glaciers — i.e., along the margin or edge of the latter. 



It must not be forgotten that the evolution of the existing 

 contours of the Australian Alps during tertiary times was. 

 dominated over large areas by the violent volcanic outbursts 

 which occurred in early Pliocene times. The immense sheets 

 of basalt which now form the Dargo, Bogong, and Paw-Paw 

 Plains — the latter at the head of the Victoria River, and 

 which sealed up the Miocene river-beds — are striking evi- 

 dences of the volcanic activity of that time ; while the deep 

 valley of the Dargo River, some 1500 feet below the Miocene 

 river-beds, is still more striking evidence of the enormous 

 erosion which subsequently took place in that valley.-f* Mr. 

 Murray, our able Government geologist, has informed us J 



* Lyell's Geology, p. — . 



t Southern Science Eecord, 1885, p. 12. 



t Geo. Sur., Vict., Vol. VI., p. 41. 



