Among the measurements made were those of currents at various 

 depths, the wind, wave height and slope. Photographs included in the 

 paper clearly show how gentle wind waves are modulated in wave 

 steepness . 



Interpretation of results includes a good correlation between the 

 total surface slope variance and the current, optimally shifted in 

 phase. The phase shift was somewhat scattered between and -90 

 degrees . 



The authors comment that their visual and photographic observations 

 are better indicators of internal waves than measurements of the surface 

 along a single line. 



This paper is followed by another (Hughes, 1978) which provides a 

 good theoretical discussion and comparison of the experiments. 



Coastal Engineering Significance. The authors provide clear documenta- 

 tion that an interaction exists between the currents induced by internal 

 waves and the surface wind waves. From an engineering point of view, 

 the results of this paper should alert wave gage users to the fact that 

 such interaction can exist and affect wave gage statistics, particularly 

 at the higher frequency end of the spectrum. 



22. JOHNSON, J.W., "The Refraction of Surface Waves by Currents," 

 Transactions of the American Geophysical Union, Vol. 28, No. 6, 

 Dec. 1947, pp. 867-874. 



Keywords . Current Refraction; Currents, Shearing; Currents, Unidirec- 

 tional; Historical Interest; Theory, Ray; Wave Height; Wavelength; 

 Waves, Deepwater. 



Discussion. When ocean waves, moving through deep still water, 

 encounter a current, moving at an angle with the wave direction, the 

 waves undergo a change in length, steepness and direction of travel. A 

 theoretical development is given for these factors in terras of initial 

 wavelength and direction, and the magnitude of current. Discussion is 

 given of the action of a coastal current in affording protection against 

 short period waves, (author's abstract) 



The early pioneers in current wave studies did not have at their 

 disposal the correct energy principle for waves on large-scale currents: 

 wave action conservation between rays. The author's equations (6), (7) 

 and (8) and Figure 4, are therefore, not correct. (A closer inspection 

 shows that the correct result, still disregarding reflection at the 

 discontinuity, is obtained by deleting the denominator (1 + m sin Ot) in 

 the last bracket in the expression just above equation (8).) 



28 



