RELATION OF STREAMS TO GEOLOGICAL STRUCTURE. 55 



( The main stream itself, north of Cooma, flows for the 

 most part in a direction slightly oblique to the direction of 

 the strike of the country, and there are indications that 

 some incipient tributaries are being determined predomin- 

 antly by the schistosity. This has suggested a means by 

 which boathook bends may be brought about in the case of 

 the tributaries of a main river which is flowing obliquely 

 across the grain of the rocks. The course of the tributaries, 

 being governed largely by the cleavage of the rocks, will 

 on one side of the river be normal, and on the other side 

 abnormal. A similar condition of affairs will obtain if the 

 main stream flows obliquely across joint systems, or across 

 fault planes or crush zones, and is a natural consequence 

 of the river system, during its normal development, seek- 

 ing the lines of least resistance and readiest erosion. 



, Professor Taylor's conception of the significance of 

 boathook bends was first enunciated in connection with 

 the physiography of the Federal Territory, where some 

 striking examples of the phenomena occur, a number of 

 the tributaries of the Murrumbidgee showing abnormality 

 of direction. For example, the Gudgenby River is a 

 normally-directed tributary of the Murrumbidgee, but 

 Guise's Creek and Sawyer's Creek, two other tributaries* 

 make boathook bends with the trunk stream, and the 

 Orroral, Nursery and Rendezvous Creeks, tributaries of 

 the Gudgenby, meet it in similar fashion. It is considered 

 that the abnormally-directed tributaries originally belonged 

 to a south-flowing river, the ancestor of the Snowy River, 

 and that a north-flowing Murrumbidgee (the divide being 

 in the Federal Territory) through head ward erosion by 

 itself and its tributaries such as the Gudgenby, breached 

 the divide and captured the Snowy tributaries. 



The author has never personally investigated this par- 

 ticular part of the State, but an examination of Professor 



