ON WAVES. 371 



Table XX. 



Observations on the Length and Velocity of Waves of the Second Order. — In 



the Sea. 



Height of wave 



e Remarks at the time of Observations. 



A fresh breeze blowing. 



Waves not easily traced. 



High seas overtake smaller ones. 



These waves came down channel. 



Long low swell. 



Small waves merged in large ones. 



Height of wave correctly measured, they 



break in 5 and 6 fathoms water. 

 Strong S.W. wind. 

 Waves running high and breaking. 

 Long low swell. 



Waves generated by wind of yesterday. 

 Waves crowd near the beach. 

 Shifting wind. 

 _ Easterly winds. 



Of these there are five which coincide with my observations and with my 

 tables, Nos. XIX. and XXI. ; and it is carious that these five are those which 

 are made in the most unexceptionable circumstances. No. II. has the remark 

 that the waves are not easily traced. No. III. has a mixture of waves, which 

 always causes great confusion and difficulty of observation. No. V. and 

 No. X. are long and low, and therefore not easily traced, and so on ; but 

 Nos. I., IV., VII., XL, XIV., are unexceptionable, and are compared with my 

 formula in the following Table : — 



XIV. 460- 42- 40-* 



We may therefore continue to use Table XXL for the velocity of sea waves, 

 unless we obtain further and decisive experiments to the contrary. It does 

 not appear that sea waves present any characteristic to distinguish them from 

 other oscillating waves of the second order which I have experimentally ex- 

 amined. 



It also follows that these waves coincide with my observations, that the 

 depth of water is the limit of the height of waves ; see No. VII., where waves 

 27 feet high, break in water ol' 5 to 6 fathoms. 



How it happens that individual large waves should ever arise in the sur- 

 face of a large sea, uniformly exposed to the action of the wind, is not very 

 obvious. Thus much is plain — that if a wave, greater than those around it, 

 be generated by a local inequality of the wind, or by one of the moving whirl- 

 pools which we know to be so common, that wave will be increased con- 

 tinually by the presence of other waves coexisting with it, for when these 

 other waves are crossing the top of this larger wave, they are suddenly ex- 

 posed to increased force by the obstruction they present to the M'ind, and 



2 B 2 



