and their Action on Floating Bodies. 97 



N.W. of Rodriguez^ met with an enormous sea rolling from 

 the S.E., about the time of the hurricane at that island in 

 Feb., 1844." (Thomson, "Law of Storms") 



Why does a wave break ? On a reference to the diagram 

 in Section 20, the reason will soon become clear. It 

 will be seen that, as the wave approaches in one 

 direction, the particles of water before it proceed towards 

 it in the opposite direction ; in other words, while an 

 advancing wave leaves behind it the particles which 

 it has raised ; it sucks up its supplies for the advance 

 of the shape from the waters in front of it. Hence, if the 

 waters in front are insufficient fully to supply the form of 

 the wave ; the form there becomes vacant, and the volume 

 of particles in the rest of the wave being still impelled 

 onward, fall over in their accustomed orbit into this vacant 

 space. A breaker, in fact, is but a visible demonstration of 

 the orbital motion of the particles, which may be observed 

 with advantage against a shelving beach ; the breaking being 

 simply the completion of the movement in the unsupplied 

 portion of the wave. 



Now, if there be good dei^tJi of water, there can be no 

 lack of front water ; because the particles beneath will 

 instantly supply the place of those in front. A wave in 

 deep water therefore meeting with a steep down rock does 

 not break ; that is, curl over, but smashes against it ; the 

 shock being the same as that which a vessel sustains in 

 oeing struck by a sea. Thus, of one of the seas which 

 struck the steamship London, and caused her ultimate loss. 

 We are told that " 100 tons of water fell on board." The 

 phraseology is correct : it is the body of a wave which 

 strikes a ship, and as in this case bursts upon her. Such 

 occurrences, not perhaps so calamitous, are common enough at 

 sea. An equally disastrous one was that which befel the U. S. 

 ship San Framcisco, in 1853. The vessel, on account of her 

 superior stability, had been selected by the American 

 Government for convej^ance of troops from New York to 

 Califoi-nia. On the voyage, she was boarded by a mighty 

 wave, which, in a moment and unawares, washed overboard 

 179 of the soldiers and officers. Although the unfortunate 

 vessel was afterwards spoken by two others, and these par- 

 ticulars gained from her, she was never subsequently seen ; 

 so that it is probable the damage inflicted by the terrible 

 stroke caused her to sink. 



Breaking, then, arises from the absence of a sufficient 



H 



