BEACH FORMATIONS AT BOTANY BAY. 



167 



the on- wash up the ridges as well as up the furrows. Sand, 

 therefore, is still deposited on the ridges, which may con- 

 tinue to increase in height while the absolute level of the 

 troughs may be lowered, and the amplitude from the crest 

 of the ridge to the bottom of the trough necessarily 

 increases. In this way is produced that succession of ridge 

 and furrow at right angles to the sea front." 1 



The present writer believed that by multiplying the obser- 

 vations convergence of light would be brought on to the 

 problem of beach origins. With this in view numerous 

 observations were made during a period of three years, the 

 fundamental conception held at the outset being that the 

 great storm determines the main beach outlines, 2 and that 

 the scallop marks a temporary disturbance of the profile of 



T|||]^]j^nTniJiiMm^iii^'?^ 



Fig. 3 — General appearance of storm beach of July 1912. 



equilibrium for the beach. For the sake of simplicity of 

 presentation the narrative style is adopted in describing 

 the observations, and it will be seen that the simple state- 

 ment of the more important observations amounts practi- 

 cally to an explanation of the forms. 



190.9. — A storm produced a wide, smooth and cuspless 

 beach of gentle slope. 



1 Vaughan Cornish, Ibid., p. 639. 



2 E. C. Andrews. The Geographical Significance of Floods, Proc. 

 Linn. Soc. N.S.W., 1907, p. 828. 



See, however, Gr. H. Halligan. Sand Movement on the Coast of New 

 South Wales. This Journal, 1906, pp. 619-640. Halligan maintains 

 that the beach outlines are due to the slight southerly current aided by 

 the northerly wind. This is a different view to that taken by the 

 present writer. 



