CHAPTER II. 



WAVES. 



Knowledge of waves necessary in designing sea-works Experiments on waves 

 Movement of particles in waves Waves of oscillation Waves of translation 

 Breaking waves Length of waves Depth to which wave-action extends 

 Effect of breakwater mounds upon waves Cresting waves Velocity of waves 

 Earthquake waves Free waves Ground-swell Forced waves Height of 

 waves Impact of waves Wave-action on beaches. 



THOSE who may be engaged in designing or constructing sea- 

 works should, as far as possible, correctly understand the nature 

 and action of sea- waves, because upon these the principles 

 which regulate the various designs for breakwaters and similar 

 works are to a great extent based. 



I propose, in considering this branch of our subject, to avoid 

 abstruse mathematical investigations, and to confine my remarks 

 within such limits as, I hope, may be of practical use. 



The theory of wind-waves, or undulations upon water, has 

 been very fully gone into by the late astronomer royal, Sir G. 

 B. Airy ; also by the Messrs. Weber, Robertson, Scott Russell, 

 and others. 



The Webers and Scott Russell, during their inquiries, carried 

 out elaborate experiments, the results of which are valuable for 

 comparison with those obtained by the aid of mathematical 

 science, with which, it is satisfactory to find, they very closely 

 agree. 



The Webers conducted their experiments in long troughs, the 

 sides of which were made of glass. In these troughs water was 

 placed which contained numerous coloured particles having the 

 same specific gravity as the water. By watching these minutely 

 when waves were made to traverse the water, the motion of the 

 particles in every part of any wave, as well as in the water below 

 it to its full depth, was clearly seen and carefully noted. 



