Gladation in the Australian Alps. 29 



glacial evidences afford in this valley, it seems difficult to 

 resist the conviction that the present smooth outlines are 

 mainly due to ice erosion. Another fact which seems to 

 support this view is, that in recent times the eroclation and 

 denudation that is taking place under sub-aerial conditions 

 presents sharper and more rugged outlines in the sides of 

 the gullies and creeks. 



In an inquiry into the causation of these ancient mountain 

 lakes or tarns, we may consider three different hypotheses — 



1. That they were caused by oscillations of the level of 



the surface, such as that produced by faultings and 

 other dislocations, and consequently might be pie- 

 glacial. 



2. That they were formed by the erosive action of glaciers. 



3. That they were formed by the building up of terminal 



moraines at the close of, or during, a glacial epoch. 

 The first of these propositions in a district which has 

 been subjected to violent convulsions, such as that occupied 

 by portion of the Mitta Mitta source basin, may appear 

 possible. For at Day's Hill — a rounded elevation situate 

 near Omeo, and at the lower extremity of the old lake-bed 

 — there is an intrusive mass of granitoid rock, which lias 

 sent out numerous radiating dykes of felso-porphyrite and 

 quartz porphyry ; while associated with the former are 

 massive outcrops of quartz. One of these quartzitic out- 

 flows, or intrusions, crosses the lower end of the lake-bed 

 near Wilson's Creek junction, and might have caused the 

 barrier to the discharge of the upper valley at this place 

 if it had been intruded subsequently to the excavation of 

 the latter; but, from the geological surroundings, these 

 intrusions are contemporaneous with the larger intrusive 

 mass at Day's Hill, which a fortiori is regarded as probably 

 Devonian, and consequently intruded long prior to the exca- 

 vation of the Livingstone Creek valley. Faultings of the 

 metamorphic schists in this valley are plentiful enough ; 

 yet no such dislocation of the surface has yet been found 

 at those points where they might be considered to have 

 produced a depression or elevation resulting in the formation 

 of existing lake-basins. It must not be forgotten that 

 eminent geologists in examining those districts elsewhere, 

 where similar geological conditions exist, and where probably 

 similar climatic influences prevail, such as the highlands of 

 Scotland (the land of breaks and faults), have remarked 

 that instances where a fault could be said to be even a 



