string could cause vibrations - would suffice as an explanation of sea 

 waves. He obtains, however, results (minimum velocity 480 cm/sec) 

 which do not agree with experience. 



(4) 

 Finally Seilkopf , more qualitatively, developed views on the 

 generation of waves; he presented the opinion that above all, the vertical 

 motions within the air were determining factors. According to Seilkopf 

 the wave motion is weakened and continuously influenced by turbulent 

 bodies of air which hit the water surface under slight, yet noticeable 

 angles of incidence, and at the same time disperse. As proof for his 

 views, Seilkopf introduces the known differences in wave characteristics 

 for cold and for warm air. While in a turbulent cold air the bodies 

 of air moved downward from a greater height directly onto the water surface 

 and rapidly generate a series of steep waves; smoother and more regular 

 wave conditions develop in ^warm air, as then there is a rolling and 

 whirling motion of a thin layer of cold air immediately adjacent to the 

 water surface. 



The abovementioned theories have only one thing in common; they do 

 not agree with the scant measurements that have been made, if a check 

 on them is possible at all. Perhaps the question of waves should not be 

 approached from a one-sided viewpoint such as suction, or wind pressure, 

 or friction, or turbulence, before clarification is made as to what ex- 

 tent each of the four causes, each surely effective in its own way, con- 

 tributes to the generation and further development of the waves. Progress 

 in this field can be expected only when new and comprehensive measure- 

 ments are made, as theory has advanced far ahead of empiricism. 



Since the generation and propagation of waves represent a typical 

 boundary problem between oceanography and meteorology, one can approach 

 the question from two sides. While oceanography strives to obtain measure- 

 ments of the shape and motion of waves, as well as, of the forces involved; 

 meteorology endeavors to study the field of wind over waves. This type 

 of observation might well make an essential contribution to the under- 

 standing and solution of the problem, since the changes of the air flow 

 over a wave-covered water surface — especially the accompanying frictional 

 losses — in combination with simultaneous wave measurements, will most 

 likely provide information about the manner by which wind affects the 

 water surface. Since waves are both moving and very irregular in shape, 

 it has not yet been possible to accurately establish the stream lines of 

 wind flow over a wave. One must be content with obtaining average wind 

 measurements, made with cup anemometers simultaneously at various heights 

 above the water surface. Such measurements are relatively difficult to 

 obtain at sea, which explains the lack of data. Over deep water, wind 

 measurements can be undertaken only from floating bodies; these participate 

 to greater or lesser extents themselves in the wave motion, depending 

 upon the relation of their dimensions to the wave length. Because of 

 this, oscillations of the wind gage are inescapable and inaccuracies 

 in the knowledge of elevations at which the measurements are taken are 

 inevitable; as these are unknown quantities it has not been possible to 

 compensate for them. 



