70 Shingle on the East Coasts of New- Zealand. 



John Coode. The main points are given in an Appendix to 

 this paper, with the results of observations by the author. 

 The two do not agree ; but the former, being applicable to 

 the locality where the observations were made, may apply to 

 some localities in this part of the world. Both are given, as 

 they may be useful to other observers. To assist in this, 

 remarks as to the chief points of difference are added (see 

 b in Appendix). 



(f.) Summary of the Foregoing Remarks on Wave-action. 



43. The following is a summary of the foregoing remarks 

 on wave-action on a beach : — 



(1.) Waves breaking on any beach stir up some of the 

 material, and carry a portion up the slope. 



(2.) The return waves wash some material down the slope, 

 the force of the waves rapidly increasing till checked. 



(3.) Return waves may, or may not, move as large stones 

 down the slope as the incoming waves carried up it, 

 depending on the slope being more or less steep than usual. 



(4.) A return wave is not destroyed on meeting an incom- 

 ing wave ; the two cross, and continue their course. But 

 the motion of the material held in suspension by the two 

 waves receives a check which tends to cause the deposition 

 of the heavier particles. 



(5.) Waves breaking obliquely on-shore cause the material 

 to advance along the shore in the direction the waves take ; 

 but waves breaking directly on-shore merely cause the 

 material to move up and down the slope without altering 

 its position laterally. 



(6.) The lower part of a wave breaking on-shore has 

 probably a backward (off-shore) motion, tending to carry 

 material away from the shore. 



(7.) Waves breaking at a distance from the shore stir up 

 the bed of the sea, and material is in consequence carried 

 away from the shore by the return waves flowing as an 

 undercurrent. 



(8.) Waves so breaking cause some of the material forming 

 the bed to rise in the water. Such material on approaching 

 the surface is likely to be carried towards the shore. 



(9.) The bed of the sea near the shore is in a state of con- 

 tinued oscillation, unless when the sea is too quiet to move 

 the material. 



(10.) If the slope of the shore be too steep for the material 



