GEOLOGICAL RECONNAISSANCE OF THE STIRLING RANGES. 109 



interval here between the original stream valleys. Possibly 

 there was a low divide running in a north and south direc- 

 tion and separating the smaller streams from the valley of 

 the Pallinnp. At what period in the history above out- 

 lined the uplift of the peneplain occurred is by no means 

 certain. It seems clear that it was after the trenching of 

 the range by the streams and it is likely that the sudden 

 beheading of them may have been brought about during 

 the major period of uplift of the plateau. 



The relation of the Porongrups to the earth movements 

 above postulated has not been examined. It is worthy of 

 note however, that, like the Stirlings, these mountains 

 present continuous summits in their eastern portion, and 

 isolated hills separated by broad valleys in the western 

 portion. This strongly suggests that, though entirely dis- 

 tinct in every detail of geological structure, the two 

 parallel mountain ranges have had a very similar physio- 

 graphic history. If the above outline is correct in its main 

 features, the beheaded remnants of what were formerly 

 much more extensive river systems are to be recognised in 

 such streams as the King, Kalgan and Hay. 



The Kalgan River calls for some description. Its upper 

 valley lies between the Stirling and Porongrup Ranges and 

 the river flows in a general east-south-easterly direction 

 until, rounding the eastern flank of the Porongrups, it turns 

 southwards and falls into Oyster Harbour near Albany. On 

 the above described physiographic hypothesis the upper 

 portion has been brought into existence at a comparatively 

 recent date. Within the broad valley part, of which is 

 occupied by the Upper Kalgan, are a number of lakes, some 

 of which at all events are moderately permanent. At first 

 sight their linear arrangement suggests that they represent 

 the remnants of a stream which formerly flowed round the 

 eastern end of the Stirling Range aud emptied into the 



