SCIENTIFIC PROBLEMS OF THE FUTURE. 677 



Fronde, mig^lit cost, with greater advantage to lier Majesty's navy and 

 to tlie nation at large as tlie leading- maritime power, than by spending 

 it in snch an investigation. It is easy to see the general line which a 

 course of exi)eriments might take. Thns one niigbt commence with a 

 real live porpoise, or, if smaller scale experiments and a cheaper plant 

 be necessary, with a salmon or a pike. Tow him through the Mater, in 

 a tank or pond, in a more or less inanimate and nonresisting condition, 

 and measure carefully by chronograplis and power meters the exact 

 horsepower required to attain a given speed or the exact time and 

 speed due to a given horsepower. Then run a steel bar through him 

 to kill and keep him rigid, and repeat the experiments with a view to 

 ascertain how far the rigidity of form would affect the result. Next 

 weigh and take an exact cast of him in plaster of paris, and cause any 

 number of models to be made, all of the same uniform pattern and 

 w(Mghted up to the same weight, but vary the material and surface 

 structure of the models indetinitely, with a view to ascertain the con- 

 ditions of minimum and maximum skin friction. Eepeat the experi- 

 ment with these various models. The result of such a preliminary 

 coarse of experiment, especially if carried out on a good-sized scale, say 

 with models of a large porpoise or a shark, could not fail to be most 

 valuable and important. It would establish incoutestably, once and 

 for all, Mdiether I am correct in believing that there is any such large 

 difference between the power required to tow a torpedo through the 

 water and that required for a fish or marine animal of a corresponding- 

 size. If so, we should learn generally how, by further systematic 

 investigation, to determine the real and essential conditions on which 

 this difference hinges. Thereby we should probably see eventually the 

 best way of minimizing fluid friction in practice. It should be borne 

 in mind that, if we could only gain a knot an hour in the speed of an 

 ironclad or an Atlantic liner for a given horsepower, the result would 

 be very im])ortant, and would amply repay any possible cost and 

 trouble in the experiments. 



It would probably be found that a smooth surface of iron or steel is 

 about the worst which we can give to our ships. For a smooth metal 

 surface has apparently the property of attracting and detaining the 

 particles of water in contact with it, whether by molecular attraction 

 or otherwise. Thereby the water in immediate contact with the vessel's 

 side or bottom is drawn along with her, and its particles communicate 

 their motion to an outer circle of particles, and so on till a vast mass of 

 water is set constantly in motion along with the ship. This is precisely 

 what we want to avoid, as the essence of the reduction of fluid friction 

 is to slip easily through the water with the least possible disturbance. 

 Herein lies, as I imagine, the great advantage of the surface structure 

 of the fish. It would probably be found by experiment that an exact 

 model of a fish in any ordinary material, as wood, iron, steel, etc., when 

 towed through the water at a given rate, would communicate motion to 



