BEACH FORMATIONS AT BOTANY BAY. 173 



high cut in upper limit of beach. Wide smooth beach of 

 gentle slope produced. 



January 31st. — Southerly wind gradually overcome and 

 strong nor' easter set in. Main breaking wave as it 

 approached the beach cut up into small and fairly evenly- 

 spaced waves, which approached shore obliquely and chased 

 each other along beach. Cusps which had been developed 

 during calmer weather of morning now rapidly cleared 

 away. Step formed at upper limit of beach produced by 

 nor' easter. 



February 1st. — Calm conditions. Cusps formed. 



February 2nd. — Mild to moderate wind from north-east. 

 Cusps formed at and near high water mark. 



During this rapid succession of strong winds alternately 

 from N.B. and S.E., it was seen that beaches were built 

 up considerably on the lower or seaward portions and cut 

 down at the upper or more landward portions ; that in pro- 

 portion as the wind was strong and along-shore (that is, in 

 this case, approximately from N. or S.) the main wave 

 front broke on the beach in short cross waves driven along 

 shore in the direction of the wind; that such waves chased 

 each other along the beach producing a current and that 

 cusps became obliterated under such conditions, but that 

 with approaching calmer conditions the beach became cut 

 away on its more seaward portion and built up on its more 

 landward portion. It was noted also that this aggrading 

 and degrading process was commenced and accompanied by 

 the formation of cusps, but that if unaltered in strength 

 for a considerable period the waves would produce a smooth 

 and cuspless beach, except for a slightly indented front as 

 to their upper or landward limits. Moreover the profile of 

 such cuspless beach was adjusted to the strength of the 

 waves. Any alteration in the weather conditions would 

 result in the breaking up of the simplicity of the beach. 



