20 GENESIS AND DEVELOPMENT 



in same proportion. His other conclusion that regular rippling has 

 an amplitude of three grains from trough to crest, seems to me rather 

 hasty. I have, however, not made any regular observations to test this 

 statement, it being of minor importance in connection with my present 

 inquiry. 



For the study of wave forms, which as a legitimate subject for in- 

 vestigation has attracted the attention of several scientists since the 

 time of Newton, Cornish has proposed 1 ) the term Kumatology 

 (/cS/xa-wave). 



Accepting this name for the sake of convenience, the writer has to 

 point out that the digressions here made into the domain of Kumatology 

 have been necessary in order to arrive at a better understanding of the 

 factors which control the movements of sand, the interpretation of 

 which is in many respects still contradictory. 



SANDY BEACHES. 



The beach may be defined as that strip of the shore which is formed 

 by the agency of waves. As a rule, it is situated between the lowest 

 level of the water and the formations produced by other geological 

 agents. 



The method of beach formation has already been indicated. It was 

 mentioned that the mechanical action of the sea is evidenced in the 

 phenomena of erosion, transportation and sedimentation. The eroding 

 action of the sea is especially prominent on steep rocky shores, and on 

 places where the difference between low and high tide is great. 



The material from the rocks eroded by the waves as well as the sand 

 and silt carried down to the rivers, sinks to the bottom of the sea and 

 is again transported by the waves and currents to the coast, there to 

 be accumulated. Although the transporting power of the waves is im- 

 mensely great, the distances to which rocks or even sand can be carried 

 is limited. In sediments of a clastic nature a sifting takes place through 

 the action of the waves against the shore, the finer material being carried 

 farther away, while the coarser is left on the shore. On very steep 

 shores, only larger pebbles and gravel are found, on lower fine sand, and 

 on very low coasts, silt. 



If we consider the movements of the sand on a low shore, we will 



1) Geographical Journal, March 1897 and June 1898. 



