BEACH FORMATIONS AT BOTANY BAY. 



169 



July 23rd. — Wind increasing. Two sets of cusps in 

 alignment and selected at random gave the following suc- 

 cessive widths : — 



30, 30, 30, 30, 30, 30, 30, 30^, 30|, 30 | 



32, 32, 32, 32, 32, 32, 32, 30, 30, 32 J paces * 



The average length of these cusps measured from apex at 



head of beach to tip of cusp was 14 paces. 



In the afternoon at low tide a new beach was seen to 

 have been in process of construction from 20 to 25 feet 

 seaward of old (1910) one. The cusps by this time had 

 almost vanished, and a bench or terrace had been excavated, 

 whose edge was sinuous in plan and corresponding to the 

 blunted cusp points which marked its beginning. The 

 bench was from 12 to 26 inches high, the higher and older 

 bench or beach (1910 beach) being 8 to 16 feet in width 

 (Fig. 5). Wind about 40 to 45 miles an hour. Breakers 

 10 feet iri height. 



Fig 5 — Ledge with scalloped front cut in storm beach by heavy swell. 



By 5*30 p.m. the cusps had almost gone and a new platform 

 was being formed below the older one. At the same time 

 the material of the beach so excavated was building up a 

 gentle slope under the water continuous with the profile of 

 the more landward portion of the beach. 



July 24th. — The ledge of erosion was carried landwards 

 and showed no cuspate indentations. Only small fragments 

 of the older higher bench left. Cuspless beach formed. 



1912, January oth. — Strong southerly wind succeeding 

 to a period of mild weather. 



