340 THE LAKE GEORGE SENKUNGSFELD, 



rivers. The old outlet (Oid Lake George River) can be traced 

 as a series of elevated river-gravels for three miles towards the 

 Yass River. The boulders, some over two feet in length, cap 

 hills nearly 300 feet above the present level of the lake-bed. The 

 economic aspects of the senkungsfeld in connection with elevated 

 auriferous alluvials, and the pastoral claims on the lake-bed are 

 traced out. 



From a comparison with the known silt-forming capacity of 

 the basin of the River Po in Italy, an attempt is made to give a 

 time-value to the silt-contents of Lake George. A period of less 

 than twenty thousand years is shown to be sufficient to fill up 

 tlie lake basin to its present silt-level under modern conditions. 

 Hence the fault and senkungsfeld may be referred to a period 

 contemporaneous with the close of the Great Ice Age in the 

 northern hemisphere, and probably to the period during which 

 the Blue Mountain folding at Lapstone Hill took place in New 

 South Wales. 



Part ii. LakeBathurst. 

 1. General Physiography. 



This Lake lies about twelve miles to the east of Lake George, 

 on the further side of the Cooma railway line, which approaches 

 within a mile of the lake near Tarago (see fig. 5 and stereogram, 

 Plate viii.). It is roughly triangular in outline, with the base to 

 the east. Quartzite hills about 200 feet high border the east and 

 south-west sides, while an area of granite extends into the lake- 

 bed on the north-west, forming a long reef connecting Rabbit 

 Island to the bluffs of the surrounding hills. 



At each corner is an area of low-lying land. To the north-east 

 a low bank separates the lake from the Bonnie Doon Morass. 

 At periods of flood the two areas form one sheet of water. The 

 southern corner receives the main feeder of the lake, known 

 locally as Chain o' Ponds. Here is a considerable extent of 

 gravels. At the western corner of the lake the gap between the 

 hills is filled in with another extensive deposit of gravels which 

 has been tapped by a railway siding for ballast purposes. When 



