488 POPULAR LECTURES AND ADDRESSES. 



is travel-ling forward through the procession from 

 its rear at a speed which is the same relatively to 

 the rear of the procession as the speed of the 

 rear of the procession relatively to the water- 

 Thus each separate wave is travelling at the ship's 

 speed, \vhich is twice as fast relatively to the 

 water as the rear of the procession of waves is 

 travelling. The wave is the progression of a 

 form ; the velocity of a wave is clearly intelligible ; 

 the velocity of a procession of waves is still another 

 thing. The penetrating genius of Stokes originated 

 the principle, admirably worked out by Osborne 

 Reynolds and Lord Rayleigh, who have given us 

 this in the shape in which we now have it. 



Now I must call your attention to some exceed- 

 ingly interesting diagrams l that I am enabled to 

 show you through the kindness of Mr. \Y. II 

 White, director of Naval Construction for the 

 Admiralty, and Mr. Edmund Froude, to whose 



1 All these diagrams, together with those from Scott Russell's 

 paper, are reproduced in the Minutes of Proceedings of the Institu- 

 tion of Mechanical Engineers, August 3, 1887. 



