president's address. 775 



geologist in his task of mapping the rocks of the country. Per- 

 haps the question of volcanic interference with our vegetation 

 could better be studied in Victoria, where the outbursts are 

 geologically more modern than in New South Wales. 



c. the distribution of plants affected by alluvial 

 deposits. 



In dealing with the question of plant distribution, one enquires 

 to what extent catastrophes by alluvial deposits have affected 

 our flora."^' I fancy that here again we have but little evidence. 

 Where plant remains (of existent plants) are found thev are 

 generally logs of timber, woody fruits, resin and such like sub- 

 stances that are practically imperishal^le if entirely immersed in 

 water, or freed from action of the air through sealing with silt- 

 like deposits. As a very general rule the leaves and other soft 

 portions of plants become, under such circumstances, disintegrated 

 into a peaty mass or decay altogether. I give one of a number 

 of recorded instances of submerged forests. A log, probably of a 

 Eucalypt, was found in cutting a deep d3dve. " The first three 

 or four feet consisted of chocolate soil, which merged into a 

 3^ello wish-clay loam, darkening again at the depth of about 10 

 feet into a peaty substance."! The deposit is further described. 



I have recently:]: given instances of fossil or subfossil resins 

 being found in Australia. They probably, in many cases, indicate 

 submergence of forests by alluvial deposits, but of the magnitude 

 of the destruction of the forests we know nothino-. 



Mr. E. F. Pittman, in a letter to me, says, " It is not an 

 uncommon thing to get fossil resin (retinite), in connection with 



* Mr. E. F. Pittman, Government Geologist, kindly informs me that he 

 knows of nothing like "extensive destruction of forests in this State by 

 alluvial deposits. We get fossil trees in most of our deep (basalt-covered) 

 leads, but nothing, so far as I know, in the way of extensive destruction." 



t Col. W. V. Legge. *' Note on timber found beneath alluvial drift at 

 Swansea (Tasmania)." Proc. R. S. of Tasm. iv. 68. 



X Proc. E. S. X.SJV. XXXV. 201, 202. 



