158 Van Diemeris Land. paet i. 



as if a volcanic eruption had taken place on the borders 

 of the pool, in which the calcareous matter was deposit- 

 ing, and had broken it up and drained it. 



Elevation of the land. — Both the eastern and 

 western shores of the bay, in the neighbourhood of 

 Hobart Town, are in most parts covered to the height 

 of thirty feet above the level of high-water mark, with 

 broken shells, mingled with pebbles. The colonists 

 attribute these shells to the aborigines having carried 

 them up for food : undoubtedly, there are many large 

 mounds, as was pointed out to me by Mr. Frankland, 

 which have been thus formed; but I think from the 

 numbers of the shells, from their frequent small size, 

 from the manner in which they are thinly scattered, 

 and from some appearances in the form of the land, 

 that we must attribute the presence of the greater 

 number to a small elevation of the land. On the shore 

 of Ealph Bay (opening into Storm Bay) I observed a 

 continuous beach about fifteen feet above hio\h-water 

 mark, clothed with vegetation, and by digging into it, 

 pebbles encrusted with Serpulas were found : along the 

 banks, also, of the river Derwent, T found a bed of 

 broken sea shells above the surface of the river, and at 

 a point where the water is now much too fresh for sea- 

 shells to live ; but in both these cases, it is just possible, 

 that before certain spits of sand and banks of mud in 

 Storm Bay were accumulated, the tides might have 

 risen to the height where we now find the shells. 1 



1 It would appear that some changes are now in progress in Ealph 

 Bay, for I was assured by an intelligent farmer, that oysters were 

 formerly abundant in it, but that about the year 1834 they had, with- 

 out any apparent cause, disappeared. In the ' Transactions of the 

 Maryland Academy' (vol. i. part i. p. 28), there is an account by Mr. 

 Ducatel, of vast beds of oysters and clams having been destroyed by 

 the gradual filling up of the shallow lagoons and channels, on the shores 

 of the southern United States. At Ohiloe, in South America, I heard 

 of a similar loss, sustained bv the inhabitants, in the disappearance 

 from one part of the coast of an edible species of Ascidia. 



