lxiii. 



The absence of marine organisms, and the fact of the deposit 

 occupying tracts varying from three to ten or more hundred 

 feet above the sea level prove in the most conclusive manner that 

 a marine origin is impossible. I would suggest that the sea- 

 worn pebbles found by Mr. Scoular in the loess of Munno 

 Para have been derived from the waste of the shingle beaches 

 of the Miocene epoch, remnants of which are still m situ at 

 a few places among the G-awler hills. 



The accumulation of the loess cannot arise from the silt 

 brought by the rivers flowing from the hills into the plain 

 without the aid of some distributing agent, inasmuch as the 

 rivers denude the loess, and only in extreme cases when they 

 overflow their banks do they distribute material' over the 

 plains, though it must be conceded that our streams may havs 

 lost their tendency to accumulate, and have in consequence 

 acted as denuding agents. But, nevertheless, the accumula- 

 tions from our short streams would have been concentrated 

 about the points where they debouched upon the plain. 



Indeed, I cannot resist the conclusion to which I have been 

 led, chiefly from topographical reasons, that the loess has been 

 deposited in a series of lakes ; a subaqueous origin fulfils the 

 required conditions, though the subaerial theory of loess for- 

 mation propounded by Bichthofen would equally account for 

 the assortment of the material. Wind plays an important 

 part in this colony as a geological agent, writes Mr. Scoular ; 

 and most of us have realised the capacity of wind as a trans- 

 porter of fine material. And it is highly probable that this 

 agent was largely concerned in the accumulation of the loess 

 of the southern margin of the Bunda Plateau (see page 116). 



One fact pointed out to me by Mr. Smeaton, confirmatory of 

 my opinion that the drift of the Adelaide Plain was assorted 

 in a lake, is that of the northerly trend of all the streams on 

 their emergence from the hills, in which their general direction 

 is to the west. My explanation of the phenomenon is as 

 follows : — In consequence of the prevalence of south-westerly 

 winds then as now, the direction of the current of the stream 

 would be deflected towards the north as its volocity was 

 slackened on coming in contact with the lake water, but before 

 commingling with it. Thus would be formed a subaqueous 

 channel which would be projected lake wards as the waters 

 slowly decreased, and along which the lengthening streams 

 would naturally flow. 



My theory of the formation of the drift requires climatical 

 conditions somewhat different from those which now obtain ; it 

 demands the operation of aqueous agents more active than now. 

 It implies a period of greater precipitation. If the loess be the 

 insoluble products of the weathering of rocks, has the material 



