116 Charles Fenner .- 



a chasm, and afforded once the lowest channel for the water, before 

 the valley now so open had been scooped out on either side by 

 gradual decomposition." When reading this interesting explana- 

 tion w^e must remember that it was written in 1836. 



The Hummocks have received a fair amount of attention from' 

 geologists. They were visited about 1886 by F. L. Krause, who- 

 figured them in the Mines Department report of that year. 

 Strangely enough, he did not visit the second gorge, that of the 

 Wando Vale Ponds, and refers to it as a " road cutting." It is- 

 evident that the Wando and the Wando Vale are at this point 

 " superimposed streams/' with wonderfully clear and convincing 

 characteristics. 



When the streams commenced their downward cutting, they were- 

 in soft tertiary material; the ridge of resistant rock lay hidden 

 less than 200 feet felow, and almost at right angles to their course. 

 With the gradual deepening of their valleys, this hard ridge was- 

 encountered, and there was nothing left to do but to "go on with 

 the Avork " ; the tAvo V-shaped gorges are the result. The great 

 contrast between the very hard rock of the Hummocks, and the very 

 easily eroded Jurassic and tertiary material under which it was. 

 hidden, have given this feature much greater distinction and 

 interest (see Fig. 5). 



General Conclusions. 



Of much interest in this area are the traces found of ancient 

 physiographic features, preserved by burial under sediments of 

 various ages and subsequently exposed by stream action. Of those 

 that were investigated in the field by the survey party, the oldest 

 may be referred to as the pre-jurassic. 



This ancient landscape has left many traces of its outlines, such 

 as may be seen in the Wando Vale district. It was evidently a 

 surface of low relief, with its ridges and valleys carved out in a 

 series of ancient resistant rocks. The most northern part of the 

 Jurassic lake system, as far as it has been preserved, embraced this. 

 area, and the accumulating sediments of this lake gradually covered' 

 the submerged landscape. 



Thus it was in part preserved until comparatively recent times. 

 Of these ridges, now partly exposed, but still with jurassics over- 

 lapping their flanks, we may mention Cashmere Hill, Bracken Hill, 

 and the ancient tablelands exposed in the Roljertson's Creek and 

 Wando gorges. Clearest of all, however, in the Hummocks (Fig. 5),. 



