Theory of Stability of Laminar Flow 473 
they quoted reliably something of the order of 25 knots, if I recall correctly. Two horse- 
power is about what the biologists will tell us the porpoise should deliver. I am quite in- 
terested that this is the figure that is gotten because this is just about right on the basis of 
the body weight and the amount of muscle and:what we know about the muscle efficiency. 
The only question is, does the porpoise go 25 knots? The 2-horsepower figure cannot ex- 
plain the 25 knots, even though it can explain the 15, so I think this is the question, are 
the speeds of the porpoises that we have just heard proverbial fish stories or are they the 
truth? I think that Mr. Burt’s question perhaps I have answered already, except for the 
Reynolds number. We have rough calculations. The limits, I am sorry, I don’t know in 
length; I haven’t made the calculation, but they lie somewhere (and these calculations are 
uncorrected by Mr. Landahl’s remarks so they are subject to some doubt) within the area of 
maybe between 107 and 10°, about 45 miles an hour (excuse my nonnautical language) for 
the coatings which have given us the best results. This is fairly consistent with our ex- 
perimental data. The calculations are rough and could easily be off by a factor of two and 
they might be off by a lot more, but we do not get 107° or anything like that. These are 
modest figures. 
