168 president's address. — section c. 



south and compelled the streams to go north or form stagnant pools 

 This slow reversal of the grade, involving a long period of base-levelling, 

 will explain the occurrence of very thick deposits of alluvium on the 

 top of the present watershed. 



One of the most remarkable features of this recently established 

 water-parting is that it cuts directly across the main lines of relief in 

 the country. The watershed is not a ridge that is appreciable to the 

 eye, but a broad plain that is crossed by ranges of hills that run at 

 right angles to the watershed. This feature indicates the relatively 

 recent date of the disruption of the older river systems, for while the 

 rivers that laid down the aggraded material are dead, their deposits 

 still occupy the old valleys and form the broad watershed that now 

 divides the drainage ; in addition to which the valley-sculpture is 

 mature and has been shaped by the streams of the past rather than by 

 the feeble creeks of to-day. 



This severance of the drainage of the interior by the development 

 of a watershed so near to the coast has rendered South Australia almost 

 destitute of important rivers. With the exception of the River Murray 

 there is no meridional river left within the country, although there 

 are abundant evidences of the former existence of such rivers, both on 

 the southern and northern sides of the existing watershed. 



On the northern side of the water-parting the slopes are longer, but 

 the streams are more erratic in their flow. The Willochra Creek, which 

 formerly flowed south to the valley of the Gulf, is now an obsequent 

 stream, which, after flowing north for 100 miles, finds its way into the 

 south end of Lake Torrens. 



Lake Frome has had an eventful history. It forms, at present, 

 the chief basin in the line of the ancient north-eastern di'ainage , and still 

 receives flood- waters from that direction. On its western side it is 

 fed by a great number of short, consequent streams that were called 

 into existence by the comparatively recent elevation of the northern 

 Flinders. The most interesting features of Lake Frome are on its 

 southern side, where from the south end of Lake Frome and continuing 

 over the Orroroo and Petersburg watershed, passing south by Laura, 

 the Condowie Plains, Lochiel, to Port Wakefield, we have one of the 

 best-defiiied, and, in extent, one of the most important of the old lines 

 of drainage. This great river system drained a vast region of the in- 

 terior, for even at Lake Frome and the Orroroo Plains evidences point 

 to the existence of a river that must at one time have rivalled the 

 River Murray in magnitude. As the result of earth movements, already 

 referred to, this great water-system has been entirely dismembered. 

 The lateral drainage loses itself in the deep alluvium of the trunk 

 valley, and, as a consequence, the drainage is peripheral and limited 

 to short isolated streams. The only considerable fragment that remains 

 at the present time is the Pasmore River (or Wilpena Creek), which 



