260 Scientific Proceedings, Royal Dublin Society. 



when the boat was placed broadside on to the waves, she travelled 

 against them. 



This result was obtained bj wave-action alone, there being no 

 perceptible current. The explanation is the same as in the case of 

 the water-soaked wood. When the boat met the waves broadside 

 on, their crests broke clean over and bej^ond her decks, and she thus 

 evaded a portion of the forward, or secondary wave-current, whilst 

 encountering the full force of the primary ; but when placed end 

 on, she received the full force of the secondary, or forward current, 

 as the portion that broke over her stern now fell upon her deck, in- 

 stead of passing over it. These experiments seem to show that a 

 floating object, if under the influence of wave-currents alone, will 

 travel in the direction of that current whose force is applied to the 

 best advantage, either on account of its action (in the case of any 

 particular object) being of longer continuance, or of greater intensity, 

 than that of the opposite current. 



It has been stated that in the event of two ships rolling about in 

 a calm at sea being in dangerous proximity, if they be headed away 

 from each other, each vessel will slowly forge ahead, and draw away 

 from its neighbour. In the case of a vessel having fore and aft 

 sails this result might be obtained by the action of the sails flapping 

 backwards and forwards ; but it seems more probable that the slow 

 propulsion of the vessel is caused by the stern, with the swinging 

 rudder, offering a greater resistance to the wave-current impinging 

 upon it than the bow offers to the opposite current. It may be ob- 

 served that before the days of steam and clipper ships the difference 

 in form between bow and stern was much greater than at the 

 present day. 



Perhaps no better proof can be advanced of the truth of my 

 proposition, that a floating object will travel in the direction of the 

 wave-current that is applied to the best advantage, than the 

 example orded b.y the natives of Hawaii in their sport of surf- 

 riding. Harper'' s Weekly, of March 17th, 1883, gives the following 

 account of it : — " The surf- riders, .... plunging beneath the first 

 wave .... rise beyond it, and swim out to sea till they meet 

 another, and then another, in each case diving just at the right 

 moment to allow the billow to pass over them. If they miscalculate 

 by one second, the surf catches them, and dashes them shorewards, 



