38 THE VICTORIAN NATURALIST. 



able subsidence must have taken place ; but at the present time 

 Tasmania is undergoing upheaval in common with the southern 

 coast of Australia. Raised beaches are well developed along the 

 shores of the estuary of the Derwent, on the southern side of the 

 island. On the north coast I have noted raised beaches at Emu 

 Bay, Penguin, Devonport and at Point Sorell. 



Such oscillations of level along the coast must have a disturbing 

 effect on the regular accumulation of the sand dunes, and I think 

 it is possible that this might account for the cessation in the 

 formation of the older dunes, and that, in considering the age of 

 our impressions, time must be allowed for — (i) the accumulation 

 of the sand between the place where the tracks were found and 

 the outermost extension of the dune ; (2) the consolidation of the 

 sand to form rock, the formation of the limestone, and the growth 

 of large timber and scrub, which could only take place when the 

 sand had ceased to accumulate ; (3) a subsidence, during which 

 a good deal of the formation has been denuded away by the sea ; 

 (4) the present movement of elevation, which would seem to be 

 going on pretty rapidly. 



Professor Tate, on the evidence of some land shells, has 

 assigned this ^Eolian formation to Pleistocene, or, more correctly, 

 late Pliocene times — a period corresponding to the Pleistocene, 

 or glacial, epoch in the northern hemisphere, not having been 

 demonstrated for Australia. Mr. Dennant, F.G.S., has given 

 cogent reasons for calling the formation recent. Professor 

 Spencer is of opinion, from a consideration and comparison of 

 the present faunas of Tasmania and Australia, that separation 

 could not have taken place later than late Pliocene times ; but 

 separation, so far as animals were concerned, might not necessarily 

 have meant separation as far as human beings were concerned, 

 primitive as the latter might have been. 



The shortest distance between Tasmania and the mainland is 

 about 190 miles, while the greatest depth in Bass Straits does not 

 exceed 50 fathoms ; so that a comparatively small amount of sub- 

 sidence or elevation would make a considerable difference in the 

 coast line. Now, if separation took place in late Pliocene times, 

 there must have been considerable differences in the coast line since 

 then. In fact, a coast line, geologically speaking, may be said 

 to be almost always in a state of unstable equilibrium, and an 

 yEolian formation such as that of which we have been speaking, 

 being essentially a coastal one, will probably share to the fullest 

 extent the vicissitudes of the coast line, and will be, at best, a 

 formation of a very transitory nature. So then, I think, there is 

 no doubt that the YEolian formation at Warrnambool which we 

 have been considering is of recent age. I am also of opinion 

 that there have been one or more minor oscillations of level since 

 the rocks in question were formed. 



