BY E. C. ANDREWS. 813 



review of the tremendous gulches of the canon cycle and would 

 see nothing phenomenal in the sluggish meanderings of a great 

 river flowing over a broad plain at sea-level. Yet in the latter 

 case the great plateau which gave birth to the stream has 

 entirely vanished from the field, while the gorgeous canons (Plate 

 xli.) incised in the high lands to-day evidence the mere start of 

 those activities which in the case of the plain have completely 

 removed the towering mountains from the landscape, involving 

 in its accomplishment the passage of untold years. 



Another important lesson will be dwelt upon when discussing 

 the origin of Sydney Harbour. 



Sjxlney Harbour, Botany Bay, the Parramatta River and Port 

 Hacking represent valleys cut in the sandstone by small streams.* 

 They had no large bodies of water with which to develop broad 

 flood plains, and contented themselves with excavating small 

 branching valleys, broadening here and there, as at Botany and 

 Botany Bay, where soft layers of rock and shale were discovered. 



At this period, when the canon cycle had progressed so far 

 that the rivers presented essentially the same features as they 

 possess to-day, (Plate xxxix., fig. g) the coast-line contained no 

 harbours, for, to retrace our steps to the close of the previous 

 plateau cycle, we shall see that the Tertiary uplift had operated 

 so as to drown the old shore-line, and a long unroughened coast- 

 line was initiated, the warping of the old plain causing the shore- 

 line to take on the appearance of a huge embayment. The 

 waves soon began cutting in close to the land, at the same time 

 building in the waste below wave-base to form the continental 

 delta. Cliffs were formed in the hard sandstone, and shoals and 

 forelands then for a period protected the land. Afterwards the 

 sea encroached still further, and great cliffs became the expres- 

 sion of the later attack of the sea on the coast. All this time 

 the streams had quietly been cutting their way into the smooth 

 uplifted plain, and from the first mild roughening of the surface 



* A study of their valleys points to the conclusion that they are rejuvenated 

 streams in part, which had been beheaded in the plateau cycle. 

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