currents, begin to dig up the bottom and further confuse the ripple 

 pattern. 



WAVES AND GUPJIMTS 



Y/ave Refraction 



A manuscript which describes a new method for the direct construc- 

 tion of way rays (orthogonals) has been completed in preliminary form. 

 The problem is considered using as a starting point the differential 

 equations which govern the ray path. The results permit a determination 

 of the error in the approximate formula: 



Aa = 4^ '^^" ^ 



which is derived by Johnson, O'Brien, and Isaacs (Graphic Construction 

 of Wave Refraction Diagrams, H. 0. Publ. No. 605, equation (2), p. 19). 

 Suggestions are nEde for improving the accuracy and ease of construction 

 of rays. 



Tsunami Recorder 



Mr. Fulk has taken the place of Mr. Osborn. Some improvements in 

 instrumentation have been carried out. During this period several heavy 

 storms were experienced. These storms ware preceded by 15-20 minute wave 

 activity on Scripps and Oceanside recorders. A nearby earthquake, off 

 San Clemente Island, did not cause any detectable tsunamis, even though 

 our instrunents are capable of recording amplitudes down to 0,1 inches. 

 Some progress has been imde in recording on magnetic tape moving at very 

 sloTiT speeds for the purpose of frequency analysis. The electric filter 

 components of the seaborne tsunami recorder have been completed. 



This research has been chiefly supported by the Office of Naval 

 Research. 



High-Frequency Wgve Recorder 



A very stable high-frequencj'', beat-frequency oscillator operating 

 at 3 to 4- megacycles has been constructed for detecting and measuring 

 ripples produced in the shallow water in the laboratory. It is adequate 

 for working with waves 0.10 mm high, and tests are under way on capacitance 

 type pickup elements. A modification of this instrument for use at sea 

 is being planned. 



Work on a ripple generator for the laboratory tank has commenced. 

 The generator will operate over a wide range of periods from about 5 

 seconds to 0.01 seconds. 



This work has been chiefly supported by the Air Force. 



39 



