318 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



In the same manner may be explained the dimensions of the ripple 

 marks on the bar of the Belon. By itself the Belon does not exist as 

 a river. Close to its mouth toward" Eiec and Moelan, in the vicinity 

 of Guilly, it is — 



A small brook, scarcely appearing to flow. 

 A thirsty giant drinks it up at a breatti. 



But between the two resisting ledges of granite the ocean has fur- 

 rowed in its direction landward a passage or fjord, at the outlet of 

 which, between the points of Eiec and Kerfany, this brook in the 

 open sea takes on at the hour of the ebb the proportions and the force 

 of an impetuous river. Its sound is considerable, and the depth of 

 the channels furrowed in the sands of the bar measures its power, 

 just as the size of the ripple marks formed opposite the point of 

 Menson reveal the currents that flow around the island of Oleron. 



To summarize, I shall formulate the following conclusions: 



1. Ripple marks are due entirely to the action of water. 



2. They are never formed on the upper beach nor on entirely 

 muddy bottoms, 



3. They appear on all parts of the lower beach, where, on the 

 sandy bottom, a transverse current cuts across the normal current of 

 the ebb. 



4. They are aligned in the direction of the transverse current. 

 Their direction, if they deviate, expresses the relation of the two 

 forces which are in action. 



5. Their dimensions are a function of the nature of the bottom, the 

 size of the grains of sand, and the velocity of the water. 



