BY R. M. JOHNSTON, F.LS. 85 
There is another condition, however, which Dr. von 
Lendenfeld * and others favoured, which also embraces 
Professor Tate’s first condition—much colder climate 
—as a contributing cause, viz., the grinding action of 
partly stranded sheets of the Antarctic drift ice, whose 
extreme northerly limits, even in the present mild epoch, 
ascend almost into the same degree of south latitude in the 
vicinity of the Cape of Good Hope. But Professor Hutton 
points out that the existence of granite in the south polar 
region has not yet been discovered. All the land at present 
known is volcanic. It is suggested, however, that Tasmania 
and New Zealand could furnish such materials, but it is 
improbable that the well-known glaciers of the western high- 
lands of Tasmania descended to sea level. 
It is almost certain, however, that at the last great period 
of eccentricity of the earth’s orbit with winter in aphelion, 
the limit of Antarctic drift ice would touch the southern ex- 
tremity of the Australian mainland when Tasmania would 
stand well within it. It is not improbable, therefore, that in 
the extreme of winter portions of the drift ice might for a 
time be stranded on the precipitous shores of Tasmania and 
New Zealand, or even on the south-western shores of Western 
Australia, long enough to receive from overhanging cliff or 
pebbly beach debris which, on breaking away in the ex- 
tremely hot and short summer, might find its way northward, 
to be again partly stranded on projecting points of the Aus- 
tralian mainland in St. Vincent Gulf, and there to leave’ in 
its trail the channelled traces of its course and part of its 
debris picked up on the coasts further south. To my mind 
this is the only reasonable interpretation which would 
sufficiently account for all the verified data so clearly brought 
forward to our notice by my distinguished friend, Professor 
Tate. 
The curved form of the encroachment of the sea in the 
Great Australian Bight also favours the idea that the well- 
known Antarctic drift current might have operated more 
powerfully in the last glacial epoch in contributing to the 
waste action which has determined its present deep bay-like 
indentation. 
It is evident that Professor Tate, who invariably uses the 
word g/acier, inclines to the view that the debvzs on the shore 
of Black Point has been carried down by an inland glacier 
descending from local mountain tablelands—now only reach- 
ing a height of about 2,300 feet—which he assumes, without 
Satisfactory evidence, to have stood 10,000 feet higher since 
the close of the miocene period, and he further objects to 
the floating ice theory, because he thinks it involves the 
necessity of assuming the swbmergence of southern parts 
* Proc. Linn. Soc., N.S.W., 1886. 
