180 GEOLOGY OF QUEEN'SLAND COAST, 



precipitate themselves over precipices in places 1,000 feet in 

 height. 



Lower down"^ the canons attain a depth of 3,000 feet, and 

 are entrenched upon their former basins, while the general 

 level of the plateau persists for as much as 30 miles 

 beyond, only broken up by these inaccessible falls, often 

 but a few hundred yards in width, and not noticeable 

 a quarter of a mile away. The traveller may wish to reach 

 a hill four or five miles distant across the gently undulating 

 plateau, but a detour of many milesf must be made in order to 

 cover the short intervening space, the gullies trenching the upland 

 being practically impassable. This points to a late rejuvenescence 

 of the plateau — the hydrographic system was disturbed, and 

 *' valley in valley " structures induced, terminating in gigantic 

 waterfalls. Withal, however, there appears to have been no 

 deflection of the streams by the formation of the anticline, since 

 the canons open along the recent stream basins into the old valley 

 and plain tracks. This then points to stream revival. 



The general east and west trend of the coastal streams shows 

 consequent drainage attendant on the seaward slope of the upland 

 during previous elevations, while the long north and south courses 

 of the head waters of such rivers as the Fitzroy, Brisbane, 

 Clarence, Hawkesbur}'- and Shoalhaven tell a tale of subsequent 

 drainage determined by the dominant meridional strike of 

 Palaeozoic rocks varying in hardness. These " strike " streams 

 point to a youthful stage in stream development. Such rivers as 

 the Hastings, now completely encircled by the "strike" streams 

 of the Manning and Macleay, may in time capture the latter, 

 owing to their steeper grade allowing them to eat back more 

 quickly into the plateau (unless checked by very resistant 

 structures the while the individual streams cut their way down 

 approximately to base level). This will mark the graded stage 



* 5 to 15 miles, 

 t Special reference is here made to the canons of the Upper Macleay 

 waters (New England). 



