Shingle on the East Coasts of New Zealand. 81 



shore winds for two or three days, the case is very different. 

 Under such circumstances, the shingle takes a perfectly 

 uniform inclination, within the limits of the tidal range, 

 and lies generally at a slope of 1 in 3 J to 1 in 4." 



(b.) Remarks by the Author on Sir John Coode s 

 Observations. 



The "on-shore winds" would, as a rule, be accompanied 

 by waves from the same, or nearly the same, direction 

 as the wind, and striking the shore obliquely or at right 

 angles as the case may be ; but the " off-shore winds," or 

 winds just along the shore, would be accompanied by waves 

 from some other direction than that from which the wind 

 might be blowing. Whether the waves strike the shore 

 obliquely or nearly at right angles — very important con- 

 siderations in relation to the movements of shingle— is 

 not known from the description given by Sir J. Coode. 

 In all cases, it would be far more satisfactory if the direc- 

 tion and character of the waves, rather than of the winds, 

 were described. The term " ground-swell" also is vague. 



The scouring away, or destructive action, mentioned 

 by Sir J. Coode, is, in the opinion of the author, really the 

 surplus shingle, which has been accumulating for a time, 

 being carried forward by waves striking the shore obliquely. 

 This gives the appearance of some having been cut out, 

 leaving a steep slope above the water-line. The sectional 

 area of the shingle in motion is simply reduced to correspond 

 with the more rapid advance of the shingle. In the case of 

 the steep slope of the Chesil Bank (1 in 3 J to 1 in 4), the 

 general action of on-shore waves, especially if following one 

 another at long intervals, must be to cut into the bank — 

 that is, to reduce the slope above the water-line. 



With regard to the effect of waves striking the shore at 

 different intervals, another observer, Mr. H. R. Palmer, 

 remarked — "that when ten breakers arrived in a minute, 

 the destructive action was but just commenced, and when 

 only eight breakers . . . the pebbles began to accu- 

 mulate." These results, it will be observed, differ from 

 those stated by Sir J. Coode. Perhaps Mr. Palmer referred 

 to the lower part of the beach, and Sir J. Coode to the 

 upper part. 



The water falling from the crest of a wave after break- 

 ing "upon the water which may be returning down the 



G 



