158 C. A. SUSSMILCH. 



Explanation .of Plates IV, V, VI. 



Plate IV. — A boulder of sandstone weighing 235 tons, lifted 

 into its present position by wave action at Bondi, N.S.W. 



Plate V. — The same boulder as shown in Plate IV, viewed from 

 the cliff above and showing the place ( x ) from which it was 

 moved. 



Plate VI. — Some effects of wave action at Bondi, N.S.W. 



BEACH FORMATIONS AT BOTANY BAY. 

 By E. O. Andrews, b.a., f.g.s. 



With Plate VII. 



[Read before the Royal Society of N. S. Wales, October 2, 1912.] 



CONTENTS. 



Introduction. — Literature upon Beach Origins. No consensus 



of opinion upon origin of Beach Cusps. Inductive method 



here insisted upon. The origin of the small temporary cusp 



is bound up in that of the several curves composing the beach. 



Thesis. — The beach cusp is a form due to the action of interfering 



waves. 

 Physical Features of Botany Bay District. 



Recent Geological History of Botany Bay. — Stream-formed 

 valleys in Trias-Jura sediments and shales. Submergence of 

 valley base by transgression of sea in Pleistocene time. Silt- 

 ing action of George's and Cook's Rivers. Formation of parallel 

 subaqueous bay bars by great storms. Emergence of such 

 bars to form wide sand flat. Formation of present beach. 



Present Beach Features. — Observations during years 1909 - 



1912 inclusive. Narrative method adopted. 

 Deductions. 

 Summary. 



