1836.] GREAT VALLEYS. 421 



their upper ends, often branch from the main valleys and penetrate 

 the sandstone platform; on the other hand, the platform often 

 sends promontories into the valleys, and even leaves in them great, 

 almost insulated, masses. To descend into some of these valleys, it 

 is necessary to go round twenty miles ; and into others, the sur- 

 veyors have only lately penetrated, and the colonists have not yet 

 been able to drive in their cattle. But the most remarkable feature 

 in their structure is, that although several miles wide at their 

 heads, they generally contract towards their mouths to such a 

 degree as to become impassable. The Surveyor-General, Sir T. 

 Mitchell,* endeavoured in vain, first walking and then by crawling 

 between the great fallen fragments of sandstone, to ascend through 

 the gorge by which the river Grose joins the Nepean ; yet the valley 

 of the Grose in its upper part, as I saw, forms a magnificent level 

 basin some miles in width, and is on all sides surrounded by cliffs, 

 the summits of which are believed to be nowhere less than 3000 feet 

 above the level of the sea. When cattle are driven into the valley 

 of the Wolgau by a path (which I descended), partly natural and 

 partly made by the owner of the land, 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. Sir T. 

 Mitchell states that the great valley of the Cox river with all its 

 branches, contracts, where it unites with the Nepean, into a gorge 

 2200 yards in width, and about 1000 feet in depth. Other similar 

 cases might have been added. 



The first impression, on seeing the correspondence of the horizontal 

 strata on each side of these valleys and great amphitheatrical de- 

 pressions, is that they have been hollowed out, like other valleys, 

 by the action of water ; but when one reflects on the enormous 

 amount of stone, which on this view must have been removed 

 through mere gorges or chasms, one is led to ask whether these 

 spaces may not have subsided. But considering the form of the 

 irregularly branching valleys, and of the narrow promontories pro- 

 jecting into them from the platforms, we are compelled to abandon 

 this notion. To attribute these hollows to the present alluvial 

 action would be preposterous ; nor does the drainage from the 



* Travels in Australia, vol. i., p. 154. I must express my obligation to 

 Sir T. Mitchell, for several interesting personal communications, on the 

 subject of these great valleys of New South Wales. 



