82 Ocean Waves 



Art. XXIX. — Ocean Waves and their Action on Floating 

 Bodies. By S. E. Deverell, Esq. 



[Read 11th September, 1871.] 



1. According to Professor Rankine, the ''energy of a 

 wave is half actual, half potential." Whatever be the exact 

 inference to be attached to this, it is plain that the power of 

 ocean waves is the impressed force of the wind. The wind 

 dies away, but its power still lives in the wave. Ocean 

 waves, in fact, are vast reservoirs of power, or fly-wheels so 

 to speak. When once set in motion, friction alone brings 

 a wave to an end ; theoretically, the motion would continue 

 to be imparted from particle to particle for ever. How small 

 the friction is, is evident from the distance to which waves 

 visibly extend when a stone is dropped into a still lake ; 

 and it has been computed to be so small that the whole 

 circumference of the earth would, in free water, be insuffi- 

 cient to destroy a wave sixty feet in height. Thus, in a 

 calm at sea, we may witness huge rollers, known by seamen 

 as a ground swell, progressing with undiminished force and 

 velocity for weeks together, though there be no fresh 

 impulse all the time ; and the earthquake waves which 

 receive their only impetus on the South American coasts, 

 travel with destructive effect as far even as the Australian 

 and Asiatic shores. 



2. Until of late years, the theory of waves received very 

 little attention, which fact is singular, considering the im- 

 portance of the subject in ship-building, the construction of 

 harbors, navigation, &c. (Ai-t. Harbors, Unc. Brit. 8th ed.) 

 Professor Airy refers the difficulty of mastering the subject 

 to the imperfection of mathematics (Art. Tides and Waves 

 Enc. Met.)* Even as late as the time of the construction of 

 Eddystone lighthouse, Smeaton spoke of waves as being 

 " amongst those powers of nature which admit of no 

 calculation." 



3. In contravention of Smeaton's opinion, is to be con- 

 sidered, that the production of waves is piu^ely a dynamic 

 process, and as such, a matter for calculation, as much as 

 are the laws of falling bodies. In fact, the researches of 

 Froude and Rankine have, despite the difficulties of the sub- 



* For a similar remark, see an article on the Pendulum, by Mr. Sang, 

 Enc. Brit. 8th Ed. 



