484 /. C. BRANNER 



On the northeast coast of Brazil I have observed cusps of 

 remarkable height. These were, however, invariably where the 

 water off shore was deeper and the waves broke with more than 

 usual violence upon the beach. 



I am not sure that I know how the two sets of waves 

 referred to in this hypothesis are produced, but I am confident, 

 that they do sometimes exist, for I have seen them. It seems 

 possible that they may be formed by an abrupt change of the 

 wind. The concentric form is given them by their entering a 

 bay around a headland. In one case the waves entering a 

 broad-mouthed bay seemed to make two sets on shore by break- 

 ing around an island in the middle of the bay's mouth. It is 

 evident that the mathematics of the work of two sets of waves 

 might be considerably enlarged upon, but this is sufficient to 

 call attention to the subject. That seaweeds have nothing to do 

 with the matter is shown by the fact that at several of the places 

 where these phenomena occur there are no seaweeds or other 

 "drift" on the beach. 



J. C. Branner. 



Stanford University, California, 

 August 10, 1900. 



