PRESIDENTIAL ADDRESS. LXXXIH 



been so strongly marked in the past as to form a very interesting 

 feature in the past physical geography of Australasia. Mean- 

 while a very brief summary must here suffice. 



As regards the fluctuations of temperature in Australia in the 

 geological past we owe it to the distinguished man, the late 

 Director of the Geological Survey of Victoria, A. R. C. Selwyn, 

 that traces of the most remarkable glaciation that the world has 

 perhaps ever seen were discovered by him in the Inman Valley, 

 near Port Victor, in South Australia. This discovery, the full 

 significance of which was not appreciated at the time, was made 

 in 1859. Mr. E. J. Dunn, the former head of the geological 

 survey of Victoria, was the first who adduced conclusive evidence 

 for the conclusion, suggested earlier by Richard Daintree, that in 

 Victoria, at Bacchus Marsh, Derrinal, near Heathcote, and indeed 

 distributed over a wide area there are glacial beds or tillites of 

 Permo-Carboniferous age. Similar beds of the same age have 

 been identified in New South Wales, and they have been dis- 

 covered on a large scale by Mr. A. Gibb, Maitland, in Western 

 Australia, where they extend right up to the tropics. They also 

 occur in India, South Africa, Southern Brazil, and in the Argen- 

 tine Republic. There can be little doubt, in view of the dis- 

 tribution on the earth of animal and plant life at this time, that 

 an immense continent probably extended right across the Indian 

 and South Atlantic Oceans as well as to Antarctica. This enormous 

 land mass would in itself, by checking any warm poleward flowing 

 ocean currents, produce great cold in the Southern Hemisphere. 

 We should have had present winter conditions in the Arctic 

 obtaining in the Southern Hemisphere also, but to a much intensi- 

 fied degree, and the cold would have been further greatly in- 

 creased, as compared with present conditions in the Arctic, by 

 the fact that there would be no relatively warm sea open in 

 summer to modify the extreme rigour of this Permo-Carboniferous 

 winter. There seems to have been a fall of temperature at this 

 time of 15 deg. to 20 deg. F. (8 deg — 11 deg. C). Possibly 

 this great difference in the geographical distribution of land and 

 water would in itself suffice to account in a large measure, though 

 not wholly, for the extraordinary glacial conditions during Pernio 

 Carboniferous time. An interesting recent discovery in this con- 

 nexion is that made by Professor W. G. Woolnough of Permo- 

 Carboniferous glacial beds with straited boulders at the furthest 

 point north on the East Australian coasts to which glaciated 

 boulder beds have been traced at Kempsey in New South Wales. 

 One interesting feature of these beds is that they conformably 

 underlie limestones in which the coral TracJiypora, a contributor 

 to the small reefs of the period, is well represented. 



Next, in descending order, we find in the Cambrian period 

 evidence of an extensive glacial age in temperate to sub-tropical 

 latitudes. Probably the contemporaneous climate was 12 deg. to 



