28 president's address. 



appears to be of a different order of events to the capture by 

 the Lower Shoalhaven of the Upper Shoalhaven. In the 

 latter case a high level stream was tapped by a low level 

 stream and then the old river, as far as its lower portion was 

 concerned, just bled to death. But the Murrumbidgee 

 drained the old Snowy upwards and backwards through one 

 of its sources while another source, though eventually inter- 

 cepted, still maintains the original direction. Undercutting 

 at static conditions would not effect this. 



Can we interpret the Murrumbidgee capture as due to the 

 development of an earth fold that rocked the old river back- 

 wards for some sixty miles 1 Such a movement would empty 

 of its stream the large but untenanted valley south of Cooma, 

 the Great Monaro Valley of Taylor, to which Mr. Slissmilch 

 first called attention. Since the Murrumbidgee above Cooma 

 still keeps to the bed by which it used to join the Snowy T 

 suggest that a movement which screwed up the valleys till the 

 watershed shifted sixty miles south, pressed down the old 

 eastern Snowy source till at Tharwa it ran backwards to the 

 Murrumbidgee and also pressed the old western source near 

 Yarrangobilly up to flow as a rejuvenated river. It is likely 

 that the two sources were originally of about the same 

 altitude. Such a movement seems of more recent date than 

 a fold which guided the Shoalhawke (and that in turn to be 

 older than another fold of which Jervis Bay may be a vestige. 



Mr. L. F. Harper has described the successive shifting 

 eastwards and lowering of the channel of the Upper Murrum- 

 bidgee.* This account is suggestive of an undulatory move- 

 ment of pliant folds rather than the breaking, faulting and 

 tilting of a series of stiff blocks figured by Taylor. It re-calls 

 the classic instance of the bed at Lapstone Hill, whose river 

 formerly drained the high quartz-felsite range towards Wom- 

 beyan. The bed of this old stream shared in the folding of 

 the Sydney-Blue Mountain area and has thus been tossed 



• Harper, Reo. Geol. Survey N. S Wales ix., 1909, p.5 



