AUSTRALIA N GLACIATIONS 219 
wether), the largest of the numerous glacially formed sheets of 
water which occur within the limits of the old ice-field. The 
Blue Lake, in the first instance, was formed as a rock basin during 
the earlier glaciation, but took its present form in the later stages. 
Its waters are dammed back on the outlet side by a huge transverse 
moraine, which is about 20 chains wide and rises to a height of 
160 feet: above the level of the lake. To test the depth of the 
lake, Professor David, in January, 1906, constructed a coracle on 
the spot, built of gum sticks, American cloth, and wire netting, and 
with this extemporized boat took soundings, which proved the 
lake to be 75 feet in greatest depth. In the following month, 
Professor David returned, accompanied by Mr. Chas. Hedley, of 
the Australian Museum, Sydney, and by means of the same frail 
coracle, obtained dredgings from the bottom, that yielded three 
species of fresh-water annelids. 
The skepticism as to the glacial origin of the smoothed surfaces 
on Kosciusko, which arose in the minds of some of the earlier 
observers, was based on the fact that much of the local rock sur- 
face gave no evidences of denudation, except what was capable 
of explanation by reference to ordinary subaerial agents. It is 
suggested by Professor David, as an explanation of this anomaly, 
that the present roches moutonnées have been protected through 
most of the year and for long ages by coverings of snow; while 
the exposed portions have been weathered into granite peaks 
and tors. The illustrations which accompany David, Helms, and 
Pittman’s papers (XXXIV) place the question of a Pleistocene 
glaciation on the highest points of the Australian continent beyond 
all doubt. 
In the determination of the approximate age of the glaciation, 
Professor David and others have fallen back on the data afforded 
by stream erosion since the retreat of the ice. At one place, in 
the Snowy River Valley, there is an old filled-up glacial lake 
(L. Andrews) with a rocky bar on its outlet side. In the U-shaped 
Snowy River Valley, the stream, since the disappearance of the 
glacier, has cut down a V-shaped gorge through a bar of hard 
granite to a depth of 60 feet. David thinks that this work of 
erosion stands for an equivalent of from 50,000 years to 100,000 
