supposed 'without bars'' and the depth of the water above 

 the crest of the bar. This ratio is 0.5° 



E. The mean ratio between the depths to the crest and to the 

 trough is l«5j however, the range of the values observed 

 is large and extends from about 1„2 to 1,9. 



F, There should exist soma relation between the velocity of 

 displacement of bottom material and therefore of the bars, 

 and the energy of the waves. 



The last three statements may have a considerable importance in 

 time of war. It was to verify these points on a beach of the simplest 

 type that we made our observations at Karen tes. We take this op- 

 portunity to express our gratitude to the Comite Central d'Oceanographie 

 et d'Etude Oes Cotes and to Mr. Gougenhein in particular, for the 

 authorization to work on the beach and the aid which has been given. 



The modifications which occurred on the beach in the course of 

 the month of August are shown on Figure 2. 



Conclusions 



The following conclusions are reached with respect to the con- 

 siderations listed above. By reason of the small range of dimensions 

 of the waves and the absence of observations during the night our 

 conclusions may be erroneous, nevertheless it appears to us reason- 

 able to deduce from our work the following results: 



Considerations A., B. and C appear to be verified without dis- 

 cussion. 



Consideration D. It is probable that the bars are displaced 

 on a relatively easily defined base "profile of a beach supposed 

 without bars", but the ratio §■ observed in laboratory "work may not 

 be verified universally in nature. For example, it is false for the 

 deep rudimentary bar found at about 1300 feet from the shore line . 

 and shown on Figure 1. It seems equally clear that when the bars 

 are in the course of displacement the crests are somewhat augmented 

 and the depth of the water over them is diminished. Any extended 

 period of calm weather appears to flatten the bars and make them 

 disappear. 



Consideration E. Wfore observations are required to reach a 

 conclusion on this point. It is clear that the ratio depends to a 

 great extent upon the factors mentioned above in connection with 

 consideration D. 



Consideration F. A study of the use of the energy equation has 

 given some interesting results but the observations made have been 

 too few to produce reliable and useful deductions. 



23 



