342 



I.OGARITHMIC SPEED-POWER DIAGRAM. 



APPENDIX. 



DEGREE OF ACCURACY OF THE LOGARITHMIC POWER DIAGRAM. 



To show that power consumed by surface friction varies almost as the 

 6.735 power of the speed for similar vessels at corresponding speeds within 

 a certain range of length, the following tabular calculations, based upon a 

 hypothecal series of ships, all similar and running at corresponding speeds, 

 are given: — 



Length. 



9 

 25 

 49 

 100 

 225 

 400 

 625 



Wetted 

 surface. 



8.1 



62.5 



240 



1,000 



5,062 



16,000 



39,062 



Friction 

 horse-power. 



.00631 

 .192 

 1.838 

 20.20 

 312 

 2,164 

 9.730 



Comparing these in pairs, the following results are obtained: — 



