Y8 Shingle on the East Coasts of New Zealand. 



(7.) Where the coast-line is irregular so that the movement 

 of shingle is likely to be arrested at times, great changes in 

 the beach may be looked for. The shingle will sometimes 

 accumulate, and at other times the excess will be removed. 

 In places the beach may be almost, or entirely, denuded of 

 shingle. 



(8.) When an accumulation of shingle takes place at any 

 point, the beach is raised. This may be called a "high" beach. 

 In this case low- water mark may extend further out from 

 the shore than usual. 



(9.) When the surplus shingle is in process of removal, 

 being carried along the coast, a flat slope is formed from the 

 water-line upwards. This may be called a " low" beach. At 

 the upper edge of this low beach is a steep slope between 

 the low beach and the high beach. This slope gradually 

 recedes further and further from the water-line till the 

 surplus shingle is entirely removed. 



(10.) A high beach will have a steeper slope, and will 

 consequently be formed of larger shingle, than a low beach. 



(11.) Shingle is lost from the beach as follows : — 



(a) By being carried below the water-line by streams, 



flowing across the beach into the sea, and by wave- 

 action at each projecting point of the beach. 



(b) By the finer particles being separated from the 



shingle, and drawn under the water-line all along 

 the coast. 



(c) By the remainder being gradually reduced to sand. 

 (12.) When the supply of shingle at any point, where its 



movement along the coast is arrested, is too great to permit 

 of the whole being reduced to sand, the shingle accumulates. 

 If this accumulation occurs against a cliff, or where waves 

 break with great force, a high bank is likely to be formed ; 

 but if the accumulation occur where the ordinary wave- 

 action on a beach takes place, the shingle is arranged in 

 successive ridges one in front of the other. 



(13.) Where there is travelling shingle, a bar will form 

 under the following conditions : — 



(a) Across the entrance to a river or lagoon. The 



depth of water over this bar is not likely to 

 exceed 8 or 10 feet at low water. 



(b) From any point where the trend of the coast-line 



suddenly changes, or from the end of any jetty or 

 other similar projection from the shore. 

 (14.) Shingle may travel in other situations at consider- 



