26 NOTKS ON MT. ANN'E AND THE WELD RIVER VALLEY. 



debouched into the Huon Valley. As the Huon deepened 

 its bed or the sea level altered, the Weld has cut through 

 and partially drained this plain. An apparently similar, 

 thouprh more extensive feature occurs on the other side of 

 the Huon, and is known as the Arve Plains. 



4. GLACIAL GEOLOGY, 

 (a) Descriptive Account. 



The vi'estern half of the area dealt with in this paper 

 and all the mountain tops in it show evidence of intense 

 placiation during the Pleistocene. In the Upper Huon 

 Valley between Mt. Wedge, Lake Pedder, Mt. Anne, and the 

 Arthur Range, the whole topography has been moulded by 

 ice action. The flatness of the plains, stretching, as they 

 do, for ten miles and more in an almost level swamp, and 

 the sinuous courses and sluggish curi-ents of the streams 

 indicate that these plains are not due to the erosion of the 

 streams that now occupy them. A recent elevation above the 

 sea could have produced such a landscape, but there is no 

 evidence of any sufficient uplift or of marine deposits here, 

 and it is not the still undrained top of a plateau, as it is 

 surrounded by lofty peaks. The rivers starting their course 

 as mountain torrents flow for several dozens of miles through 

 plains in a very mature stage of erosion and then finish 

 their course in a more or less juvenile stage. Clearly an 

 "accident" has occurred to the drainage of the Huon and 

 Serpentine Plains, which do not present the characteristic 

 features of river erosion, and the cause of that accident has 

 been the intervention of the ice sheets and glaciers of the 

 Pleistocene glacial epoch. 



The general aspect of the whole region, the sides of the 

 hills rising in a clean curve nearly vertically out of the 

 plain, the U-shaped gaps between adjacent hills when they 

 occur close together, the absence of water-worn valleys in 

 the extraordinary level plain, all support this view. Some 

 low hills break the surface of the plain at considerable inter- 

 vals. These are almost always narrow, steep-sided ridges, 

 apparently scraped bare by ice. The lower slopes of the 

 main mountains and spurs are in general smooth and 

 decidedly concave in section — ordinary water-worn hills being 

 convex, streams gathering strength to erode as they descend 

 — while the more elevated crests are extremely rugged 

 above the 3,000-foot contour with picturesque pinnacles and 

 crags. The outstanding spur of the Frankland Range 

 that rises to the south-east of Lake Pedder is decidedly Tind- 

 like when viewed from Mt. Anne. 



