Section C. 



GEOLOGY AND PALEONTOLOGY. 



Address by the President, 

 T. W. EDGEWORTH DAVID, B.A., F.G.S., 



Professor of Geology and Physknl Geography, University of Sydney, N.S.W. 



The subject of Volcanic Action in Eastern Australia and 

 Tasmania, with special relation to sedimentation and slow 

 movements of the earth's crust, has been chosen by the author 

 as the subject of the present Address, partly as a sequel to 

 the Presidential Address delivered by Professor Hutton 

 at the meeting of the Geology Section of the Association at 

 Melbourne in 1890, and partly on account of the great local 

 interest which attaches to the vast development of volcanic 

 rocks in the immediate neighbourhood of Hobart, and over a 

 very large area in the south-eastern and northern portions of 

 I'asmania, The author proposes to review briefly the 

 evidences of volcanic action in past geological time in the 

 portion of Australasia above mentioned ; then to adduce 

 some theories which may account for such phenomena, and 

 especially to inquire into their possible relation to sedimen- 

 tation. 



As far as the author is aware, the oldest rocks in Eastern 

 Australia, which have been proved indisputably to be of 

 volcanic origin, are the Snowy River porphyries of Eastern 

 Victoria. 



Mr. A. W. Howitt, F.G.S., tiie Under Secretary fur Mines 

 in Victoria, refers this group of volcanic rocks either to the 

 top of the Lower Devonian Series or to the base of the 

 Middle Devonian. The series consists of felstone porphyries, 

 felstone ash, and agglomerates.* 



I |The fragmentary portions vary fi-oni a fine microscopic 

 dust up to pieces several feet in diameter. The series is 

 about 20 miles wide, 70 miles in length, and upwards of 

 2000 feet thick. 



* Victoria : Geology and PhyScal Geography, by Reginald A. F. Murray 

 Government Printer, Melbourne, 1887. — pp. 48-52. 



