32 



A FURTHER NOTE ON THE TOPOGRAPHY OF LAKE 

 FENTON AND DISTRICT, 



NATIONAL PARK OF TASMANIA. 



By A. N. Lewis, M.C, LL.B. 



(With 2 Text Figures.) 



(Read 8th May, 1922.) 



Visits to the Mt. Field Plateau since compiling: my pre- 

 vious paper (Lewis, 1921) have confirmed all the observa- 

 tions therein contained, especially as amplified and explained 

 by Professor Griffith Taylor, D.Sc. (Taylor, 1921). 



Lake Fenton is a paradox. It lies about 3,400 feet 

 above sea level, almost at the top of a mountain ridge in 

 the drainage basin of the Broad River. But the outlet, in- 

 stead of draining down the slope of the hill to the river, 

 breaks through the main ridge of the plateau in a gorge 

 500 feet deep into the Tyenna Valley. The lake is clearly 

 of glacial origin, but the reason for the direction of its over- 

 flow requires fui-ther explanation. 



As I explained in my previous paper, the general water- 

 shed of the plateau runs in a westerly and noi'th-westerly 

 line from ]\It. Field East, through Seager's Look Out, Mt. 

 Monash, to the long ridge of Mt. Mawson. The Broad River 

 drains this plateau, and has pushed its tributaries right to 

 the edge overlooking the Tyenna Valley. On the southern 

 side of the watershed the water that falls on the slope runs 

 away in many mountain rills down to the Tyenna Valley, 

 from which the land rises 3,000 feet veiy steeply to the 

 edge of the plateau. The surface of the plateau slopes down 

 gently to the northward from its southern edge, and the 

 Broad River runs through its lowest valley. 



Topographically, Lake Fenton belongs to the Broad 

 River drainage basin. The land slopes away naturally from 

 Seager's Lock Out and Mt. Monash, across Lake Fenton to 

 the Broad River Valley. But just at the site of Lake Fenton 

 the main ridge ha.s been c.it through in a huge gap through 

 which the lake empties itself, in exactly the opposite direc- 

 tion from that which appears natural. 



