ii 



intelligence than the road-maker. There are those who think otherwise ; 

 who consider that the latter frequently displays the broader and more 

 masculine intellect. However this may be, all rational men agree in 

 awarding the highest meed of praise to those who can both find the path 

 and make the road, — who can say to the little children of science, so far 

 can you follow me — and to the maturer minds, from that point you may 

 extend my paths. Of these men was Eankine. 



Eankine's most important contributions to science are in the dynamical 

 theory of heat, in the theory of the steam-engine, in that of waves in 

 liquids, especially of sea-waves, and on the resistance and rolling of 

 ships. He was among the earliest students in this country who were 

 able to understand what was meant by thermodynamics. He contributed 

 largely to the extension and settlement of the theory, and, probably to a 

 greater extent than any other person, to its reduction to rules adapted 

 to the practice of engineers; indeed he may be considered one of the 

 founders of the science. In the study of waves in liquids, he and Mr. 

 "William Froude appear to have been the first persons who successfully 

 worked out a possible theory of waves of finite displacement in the sea : 

 all the previous researches were either incomplete in theory or limited 

 to infinitesimal disturbance. Eankine and Froude, working indepen- 

 dently of one another, appear to have been the first to arrive at a definite 

 demonstration of the mechanical possibility of the trochoidal wave. 

 They were not the first to suggest that the trochoid was the clue to the 

 geometry of the sea-wave : Grerstner and Scott Russell had already done 

 that ; but it was Froude, in the ' Transactions of the Institution of 

 Naval Architects,' and Eankine, in the ' Transactions of the Eoyal 

 Society,' who first gave proof that it complied with all the conditions of 

 fluid motion, except that of the absence of molecular rotation. 



His study of the resistance of ships appears to have been suggested to 

 him by an application addressed to him and to Professor (now Sir 

 William) Thomson by his friend James Eobert Napier, for advice as to 

 the power necessary to propel vessels of any form. Professor Thomson 

 then called attention to the defect in existing theories, with reference 

 to the resistance of water to a ship's progress, from not taking account of 

 the viscosity of the fluid. Professor Eankine stated that if the re- 

 sistance outside a ship was the same as that inside a water-pipe, the 

 power required to propel a certain vessel would be so and so, naming a 

 power of about two thirds what Mr. Napier had estimated to be 

 necessary. Alluding to this, Professor Eankine wrote, in August 1858, 

 to the Philosophical Magazine (ser. 4, vol. xvi. p. 238) : — " In the course 

 of last year there were communicated to me in confidence the results of 

 a great body of experiments on the engine-power required to propel 

 steamships of various sizes and figures at various speeds. From those 

 results I deduced a general formula for the resistance of ships having 

 such figures as usually occur in steamers, which, on the 23rd of December, 



