of the Island of Tasmania. 151 



tapering stems of extraordinary height; while the under- 

 growth is of moss and fern, and shaded by almost impassable 

 thickets of Pomaderris elliptica, Fagus Cunninghami, and 

 tree ferns (Dicksonia antarctica). The sides of the smaller 

 streams are thus nearly always surrounded by forest. But 

 there is a great difference between the dense vegetation of 

 the comparatively level and open rivers of the plains and 

 those which are supplied from the mountain gullies. The 

 latter are all completely shaded in by a thick growth of 

 forest extending for a long distance on either side. The 

 tablelands are, as already stated, grassy, and free from 

 timber; and in all the country to the south and west, between 

 the densely wooded gullies, the land is open, and clothed 

 with a sedge called button grass (Gymnoschcenus sphcero- 

 cephalus, Hooker) and Xyris gracilis, Schizcea bifida, and 

 many mosses, fungi, and lichens. In all the elevated regions 

 of the western and southern mountain systems the soil is 

 open, poor, and wet. The snow lies upon it for many months, 

 and its humidity and exposed situation render it worthless 

 for settlement. 



I will now describe the various geological formations 

 which form the mountain S} 7 stems of the island. 



Granite, syenite, and porphyritic granite are well repre- 

 sented on the east coast at George's Bay. It is also found 

 at Mount Bischoff, and occasionally along the Eldon Range, 

 near Ben Lomond, Mount Barrow, and other places. Its con- 

 nection with other formations is not well made out. As a 

 rule it does not play the most important part in the geology of 

 Tasmania. It does, however, contribute a very important 

 item to the mineral richness, as it is in connection with the 

 granite formation that the remarkable deposits of tin have 

 been found. 



Metamorphic Bocks. — It is probable that the base of most 

 of the mountain ranges to the westward consist of 

 metamorphic rocks. They are principally varieties of 

 quartz rock and schist, which appear to alternate and pass 

 into one another. They are especially developed in the 

 country about the Eldon, Arthur, and Frankland flanges, 

 Frenchman's Cap, Mount Murchison, &c. The mica schist, 

 according to Mr. Charles Gould, consists of quartz and mica 

 in varying proportions. These minerals are sometimes 

 arranged in alternate laminas, while at others the quartz 

 is aggregated into nodules, which are imbedded in soft 

 micaceous, or occasionally chloritic schists. Those varieties 



