20 



and southern waters of Tasmania. Of the higher animals we 

 can only conjecture, but we are at least sure that many of the 

 marsupial tribe, allied to the existing Wallaby and Kangaroo 

 Eat, abounded in the scrub close by. 



This imaginary scene may fairly be taken to represent 

 what we know of the earliest stage of this ancient lake of the 

 Derwent, which I consider to belong to the same horizon as 

 the lower zone of the Launceston Tertiary Basin. 



The second stage is indicated by the disturbances caused 

 by repeated eruptions of feldspathic basalt along the margin 

 of the old lake, and spreading over a portion of its floor. 

 Cornelian Bay Cemetery and One Tree Point represent this 

 stage clearly. It is evident that a very long period must 

 have elapsed between the formation of the first sedimentary 

 deposit of the lake and the period when the eruptions began. 

 It is also clear that the period of disturbance must have been 

 of long duration. The Sandy Bay deposits are good illus- 

 trations of the first period referred to. The second stage I 

 recognise as the equivalent of the middle zone of the 

 Launceston Tertiary Basin. 



The third stage marks the distribution of the gravel beds 

 with their agates, jaspers, cornelians, and fossil woods. At this 

 time the lake must have been rapidly shallowing. It is even 

 possible that the mere horizontal advance of the sea is alone 

 necessary to explain the final draining of this ancient fresh- 

 water system. If the outer lip of this lake basin was pierced 

 by the slowly advancing sea, it would sufficiently account for 

 all the appearances with which I am now acquainted. 



There is no need to assume a general depression of the 

 land surface or a subsequent elevation, although I do not 

 wish to be understood to mean that a slight alteration of the 

 general level may not have been associated with the causes 

 already cited. 



The horizontal encroachment of the sea in the direction of 

 its present limits must have been very slow, and long enough 

 in duration to admit of a complete transformation of the 

 characteristic flora and fauna of the period. 



When we reflect that the changes which take place within 

 our own observation, with respect to existing animals and 

 plants, are so slow and imperceptible that many otherwise 

 intelligent minds have a rooted repugnance to recognise the 

 facts which support the evolution hypothesis, we can, even 

 better than in terms of years, estimate the immensity of 

 time which separates the extinct species of vegetation of even 

 the upper members of the lake system from the artificial 

 shelly accumulations of recent origin which now alone remain 

 to give evidence of the extinct Tasmanian race. 



Such then is the story which I have been enabled to 



