164 E. C. ANDREWS. 



action of the George's and Cook's Rivers when in flood, 

 and with the progress of time, either aided or not by this 

 action, the storm waves pulsed through the heads and 

 formed the bay bar AB, tying together two headlands in 

 the bay in the manner suggested by the section (Fig. 1). 

 Simultaneously the main bay bar CD was formed farther 

 out in the bay as a result of repeated gale action. These 

 ridges gradually increased offshore by means of parallel 

 growths during record storms. But between the shore- 

 line and the bars AB and CD, long strips of relatively deep 

 water remained. It is probable that none of these bay bars 

 ever reached the surface of the bay. 



During recent historic times these sand bars and flats 

 emerged from the bay to an average maximum height of 

 16 - 20 feet above low water mark. By silting action, after 

 the emergence of the bay bars as dry land, the interbar 

 areas became converted into swamps, while Muddy Creek, 

 breaking through the sand bar AB, kept this portion within 

 tidal influence. 



The argument for the subaqueous as opposed to the sub- 

 aerial origin of these forms is based on the peculiar dis- 

 position of the sand ridges and swamps, these lying approxi- 

 mately parallel to the present beach, and not at right angles 

 to the direction of the dominant winds, the persistence in 

 length of the main bars and the general accordance of the 

 sand ridge summits. If of aeolian origin the bars should 

 be rather in the form of dunes pointing to the north-west 

 or north-north-west, they should be much less regular and 

 much more massive and they should not possess such 

 accordant summits as the forms under consideration. 1 



An examination of other low-lying plains of sand in the 

 Sydney district tends to strengthen this opinion. Thus the 



1 G. H. Halligan. Sand Movement on the New South Wales Coast. 

 Proc. Linn. Soc. N.S.W., 1906, p. 62] 



