of the Island of Tasmania. 147 



As in south-east Australia, the most precipitous portions 

 of the ranges are on the east side. They seem to abut upon 

 the ocean at various places in the whole mountain chain, but 

 this peculiarity becomes more marked towards the south, 

 and most of all in Tasmania. On the east side the 

 mountains confront the ocean with little or no intervening 

 level ground. On the north side there' is a considerable area 

 of low- lying ground between the sea and the mountain 

 ranges. This is not a level tract. These are spurs from 

 the elevated plateau which divide the basins of the Tamar, 

 the Mersey, the Forth, tlie Leven, and other rivers. All 

 these streams empty upon the north side of the island; they 

 have their origin in the elevated tableland, but descending 

 from that have a long course through the comparatively 

 lower land which intervenes between the plateau and 

 the ocean. In some of the valleys or river basins there 

 are patches of tertiary rocks. Some are fresh- water de- 

 posits, with abundance of leaves and plant impressions. 

 Some tertiary marine shells have also been found. The 

 dividing ridges between the streams are the usual paleozoic 

 rocks of the Cordillera. As the same rocks are found upon 

 the tableland, there must be a great fault, or a series of 

 them, between these sedimentary rocks and the more elevated 

 plateau This causes the inclined edges of the fossiliferous 

 rocks to abut upon the greenstone masses of the interior. 



The plateau or tableland occupies the centre, or perhaps a 

 little to the north of the centre, of the island. In its highest 

 portion it is over 4000 feet above the sea, and the average 

 is not much under that height. It is distinguished by 

 possessing large and deep lakes of fresh water. The Great 

 Lake has a length of thirteen miles, with a maximum width 

 of eight miles, and an average of three to four. It covers 

 an area of 28,000 acres. There are besides Lakes Sorell, 

 Crescent, St. Clair, Arthur, and Echo. They are the sources 

 of all the important rivers in the island. This tableland is 

 for the most part covered with beautiful grass lands, with 

 no important mountains in their vicinity, unless in the case 

 of Lake St. Clair. It is probable that the descent from this 

 plateau is by a series of terraces (notably the Middlesex 

 Plain and Mount Bischoff plateau, averaging 1800 to 2000 

 feet); and there are also in various parts of the island other 

 tablelands of smaller extent and lower elevation. Thus 

 Lakes Tiberias, Dulverton, and Tombs, on the east side of the 

 island, are similar features. They are seen again in the south- 



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