AND OTHER WATER WAVES 165 



however,, the mere action of a small swell from 

 the offing appears to bring the sand in here when 

 the slope of the shore has been reduced almost 

 to nothing. The shoreward action does not then 

 cease with the breaker ; for the waves, breaking 

 far out, produce another kind of wave, the bore, 

 a wave of permanent form with a precipitous foam- 

 ing front. There is always a procession of these in 

 advance of the breaker -line, and they thin them- 

 selves from less and less to nothing as they advance 

 to the shore. Sand -ripples over which they pass 

 (when not wholly obliterated) are no longer sym- 

 metrical, but face shorewards, and, presumably, 

 travel shorewards. The action of these waves upon 

 quickly subsiding material is predominantly shore - 

 wards, being an exaggeration of that already 

 described for waves about to break. 



After a time of fair weather, a moderately sloping 

 foreshore and a beach of clean sand is once more 

 formed here, and equilibrium is re-established for 

 such weather, the slope being a measure of the 

 excess of shoreward over seaward action proper 

 to the waves. 



All this process which I have described differs, 

 however, but little from that already specified for 

 shingle, and the reader will naturally be more in- 

 quisitive as to the explanation of the reversal of 

 this in prolonged rough weather. 



