Geological Notes, Tasmania. 129 



taken in conjunction with the cliaracter and position of the 

 matrix, mark the deposit as a true till or ground moraine. 



Lake Dixon, to all appearance, is very shallow. Its edges are 

 not deep, though some of the slopes above are decidedly steep. 

 Reeds grow in the lake for some distance from its northern 

 extremity. It is quite probable that Lake Dixon is a morainic 

 lake. 



As to the age of this ice action, it is difficult to say more than 

 that everything tends to show that it has been the work of 

 recent glaciers. The finding of erratics still resting on the 

 polished surfaces is suggestive, while the valley seems to have 

 altered but little since the time when the river of ice slowly 

 made its way downwards. 



At tirst sight it seems strange that we have such direct 

 evidence of glaciation in this valley of the Lakes Undine and 

 Dixon, while the evidence in some of the surrounding valleys is 

 negative. It is of importance, however, to remember that 

 elevation is but one condition essential for the former glaciation 

 in this region. Important elements to be considei*ed are the 

 contour, size, and length of the valley. This valley seems to be 

 admirably adapted, not only for being a gathering-ground of 

 snow, but also for the conversion of this snow into a glacier. 

 •Surrounded as it is by mountains rising to a height of 2000 feet 

 above its level — itself 2000 feet above the sea — snow would 

 inevitably collect to some considerable extent, while the slope of 

 the valley would cause sufficient movement in the glacier to 

 enable it to carve and polish and scoop the hard rocks. Added 

 to this, the glacier would be supplemented by tributaries 

 descending from the minor valleys to right and left. At present 

 the snow in winter must be considerable. The last of the 

 previous winter's snow had not melted on Olympus by the end of 

 January, so it is not necessary to assume a very extensive fall of 

 temperature to account for perpetual snow in these regions. 



The geology of Lake St. Clair has already been described by 

 Mr. Officer (Trans. Roy. Soc. Tas., 1893). The main features 

 are similar to those about Mount King William, the mountains — 

 e.g., Olympus, Byron, Cuvier, Ida, etc. — consisting of a base of 

 sandstone (Permo-Carboniferous), capped by greenstone. The 

 possibility of its being a glacial lake is worth considering. There 



