BY PROFESSOR STEPHENS, M.A. 549 



basin. However, the Capertee Eiver, joined first on the left by 

 the Umbiella Creek, and then, about 12 miles N.E. of the Station 

 by the Coco, or Coco Coeai, takes the name of Colo, and enters 

 an impassable ravine, Sir John's Mouth, down which it flows for 

 nearly twenty miles until its junction with the AVolgan, which 

 rises near the head of the Cox. 



A small portion of the upper part of the AVolgan is thus 

 described by Darwin — " When cattle are driven into the valley 

 of the Wolgan, by a path (which I descended) partly cut by the 

 colonists, they cannot escape ; for this valley is in every other 

 part surrounded by perpendicular cliffs, and eight miles lower 

 down, it contracts, from an average . width of half a mile, to a 

 mere chasm impassable to man or beast."* Through a similar 

 chasm, 20 miles further down, the Wolgan joins the Colo, which 

 continues an almost subterranean course, receiving, 12 miles lower, 

 the Wollungambe from Mounts Wilson and Tomah, until, about 

 eight miles further, it at last emerges into more tolerable country, 

 finally joining the Hawkesbury about 10 miles below. 



These phenomena are frequently repeated in the Blue Moun- 

 tains. We see long and wide valleys which suggest the action 

 of erosion on a gigantic scale, but are now drained through gorges 

 which are often absolutely impassable, and through which it is 

 inconceivable — in fact impossible — that such a volume of detritus 

 could have passed as would correspond to the amount of supposed 

 excavation. The friction of innumerable multitudes of travelling 

 pebbles and sands (the chief materials of the rocks which are 

 assumed to have been removed by erosion and denudation) would 

 surely in the long course of ages have worn broad and open 

 channels for their passage. Yet we do not find this to be the 

 case. The Wollondilly and Cox Eivers, leaving the extensive 

 basins which they drain, and passing through contracted and 

 deep ravines, unite to form the Warragamba, the course of which 



* Geological Observations, p. 152, Ed. 1876. 

 Kl 



