ILLUSTRATIONS 



Figures in Text 



Figure Page 



U. S. Navy destroyer in a heavy sea Front ispiece 



1. Movements of beach grass in a low swell 3 



2. Orbital movements of water particles in wind waves 4 



3. Movements of water particles in shallow water 4 



4. Ripple marks at the bottom of the Gulf of Maine . 12 



5. Graph showing the theoretical relationship between wave lengths, 



velocities, and periods in deep water 30 



6. Isobaric distribution over the North Atlantic . _ . . _ 3!) 



7. Diagram showing the relative directions of the advance of waves and 



of winds by which they are generated 40 



8. Directions of winds and waves in a tropical hurricane . 40 



9. Profile of a wave of trochoid form ___ . _ 43 



10. Profile of a trochoid wave showing angle of a boat at steepest part of 



crest 44 



11. Theoretical profile of steepest possible wave 44 



12. Profiles of waves of different degrees of steepness 45 



13. Smaller waves running on top of an older swell 47 



14. Moderately heavy sea in the North Atlantic . ... 4S 



15. Surface configuration of the front of a wave about 19 feet high 4'.) 



16. Surface configuration of the back of a wave 27 feet high 50 



17. Peaks developed by interference 52 



18. A moderately high and breaking sea 04 



19. Back of the crest of a high and breaking storm wave __.. . 05 



20. Diagram to show changes in directions from which swells come with the 



advance of a storm center . .... 08 



21. Graph showing the theoretical alteration of waves advancing over a 



shoaling bottom __ 103 



22. A breaker of the plunging type, showing stages of development _ 111 



23. Oblique view of a breaker of the plunging type 112 



24. Aerial photograph of breakers of the plunging type 113 



25. Breakers of spilling and plunging types 114 



26. A breaker intermediate between plunging and spilling types 116 



27. A wave of translation preceding a breaker up a gently sloping beach. _ 117 



28. Heavy surf beating against the boulevard at Winthrop, Mass 119 



29. Surf almost wholly enveloping Minot's Light, Massachusetts . 120 



30. Breakers caused by swells which are hardly visible offshore 125 



31. Pattern produced by breakers from different directions 128 



32. Waves breaking farther out at the mouth of a tidal inlet than along the 



neighboring beach 120 



33. Breaker developing against the base of Minot's Light, Massachusetts _ 133 



34. Wave breaking close to the tide line on a steeply sloping beach . 134 



35. Surf extending 5,000 feet out from shore 130 



30. Surf developing over bars, with and without surf on the beach .. . 137 



37. Surf with two chief lines of breakers off the Hawaiian Islands __ 138 



38. Moderately heavy breakers on two bars and on the beach behind 



them 139 



