Newman 



the transverse waves are examined, but the difficulties of carrying 

 out full-scale measurements in an ambient wave system are well 

 known. (In spite of their appearance to the contrary. Figs. 3-5 

 were made early in the morning of a relatively calm day to ensure 

 little ambient wave motion. The low rising sun in the model photo- 

 graphs is explained similarly!) 



Turning to the wavy wall tests described in Section IV, we 

 have attempted, without success, to verify a theoretical anomaly -- 

 Howe's phase-jumps. It Is an open question whether this failure is 

 due to experimental error (an obvious possibility Is the effective 

 modification of the wavy wall shape due to viscous effects) , or If , 

 in fact, the phase discontinuity obtained by Howe Is a consequence of 

 pushing Whltham's slowly varying finite amplitude technique too far, 

 with a solution which Is not always slowly varying but contains local 

 "singularities" or "shocks," It Is not likely that this question can be 

 answered by further experimental work, unless possibly a viscous 

 correction can be Incorporated In the model's shape (to allow for a 

 turbulent boundary layer In the presence of a slowly varying sinu- 

 soidal pressure gradient!). 



Finally, In Section V, we have outlined a nonlinear analysis 

 of the Kelvin wave system which predicts an Instability along the cusp 

 line, but for which (unlike Howe's Instability) the conclusion depends 

 critically on a delicate avoidance of algebraic errors. Having thus 

 gone out on a limb, I can only express the hope that Independent 

 verification is soon forthcoming. 



VII. ACKNOWLEDGMENTS 



The three experiments described here were carried out with 

 the generous assistance of many persons. The full-scale photographs 

 of the UNCATENA were made by Mr. F. Claude Ronnie of the Woods 

 Hole Oceanographic Institution; the Woods Hole Oceanographlc Insti- 

 tution also furnished the aircraft for these tests and the services of 

 Mr. Robert Weeks as pilot. The subsequent experiments were per- 

 formed by several MIT graduate students: David MacPherson and 

 William McCrelght built the fiberglass mold and model of the 

 UNCATENA; Albert Bradley kindly loaned his radio control system; 

 and the model completion and testing was carried out by Charles Flagg 

 and Nan King, with photographs made by Ronald Walrod. Messrs, 

 Flagg and King also built and tested the wavy wall model, and photo- 

 graphs of this test were again provided by Mr, Walrod. The propeller 

 for the UNCATENA model was kindly loaned by Professor Daniel 

 Savitsky of the Davidson Laboratory, Stevens Institute of Technology, 

 and the wave probes used for the wavy wall test by Professor Jerome 

 Mllgram of MIT. 



538 



