BY G. H. HALLIGAN. 621 



A similar movement has taken place at Jervis Bay, where the 

 North Head — -originally an island — has been joined to the main- 

 land by sand drifting from the north after first filling the Shoal- 

 haven Bight. 



Coming nearer home, we have all that stretch of coast between 

 Wabung Head and Tuggerah Lakes entrance formed to its present 

 shape by sand-movement; and Norah Head, which was once an 

 island about eight miles from the shore, now forms a salient point 

 on the coast. 



Tuggerah, Minmorah and Macquarie Lakes are but lagoons not 

 yet filled up, though the onshore winds which blow the sand from 

 the beach, the discbarges of sediment and debris by the streams, 

 and the growth of saltwater weeds are slowly but surely carrying- 

 out their functions. The lakes will become marshes, the marshes 

 swampy land, and then, in due course, good agricultural land for 

 the use of future generations. There does not appear to be any 

 necessity to assume a movement of elevation to account for the 

 land thus formed. Where borings have been taken for bridges, 

 harbour works, etc., over the area mentioned, they invariably 

 show coarse or fine sand of marine origin from about three to 

 twenty feet above high water to the bottom, with a thin capping 

 of humus or carbonaceous soil. 



As sand dunes sometimes reach a height of 100 feet or more, 

 and have an average height on this coast of about 20-25 feet, it 

 appears probable that the wind and sea are solely responsible for 

 the elevation of the land referred to. 



The form of the coast-line of New South Wales indicates a very 

 slow negative movement of the land, and there is nothing, from 

 a physiographer's standpoint, which necessitates the assumption 

 that a positive movement has taken place within recent geological 

 time. 



The principal factors which govern the movement of sand and 

 shingle on the littoral are : (1) ocean and tidal currents; (2) wave- 

 action; and (3) wind. On any coast where the tidal range is 

 larjje, say from 12 to 20 or more feet, the flood tide is the pre- 



