﻿106 
  Mr. 
  J. 
  H. 
  Michell 
  on 
  the 
  

  

  The 
  formula 
  was 
  tested 
  by 
  drawing 
  a 
  system 
  of 
  continuous 
  

   isothermals 
  giving 
  pv 
  plotted 
  against 
  v— 
  f, 
  and 
  then 
  the 
  

   experimental 
  values 
  were 
  put 
  in 
  as 
  dots 
  ; 
  there 
  is 
  on 
  the 
  

   whole 
  a 
  fair 
  agreement 
  between 
  calculation 
  and 
  experiment, 
  

   as 
  may 
  be 
  seen 
  on 
  inspection 
  of 
  the 
  diagram. 
  It 
  is 
  generally 
  

   difficult 
  in 
  these 
  investigations 
  to 
  know 
  how 
  much 
  may 
  be 
  

   reasonably 
  allowed 
  for 
  experimental 
  errors. 
  Fortunately 
  in 
  

   this 
  instance 
  we 
  have 
  a 
  clue 
  to 
  guide 
  us, 
  as 
  Messrs. 
  Ramsay 
  

   and 
  Young 
  in 
  testing 
  their 
  linear 
  law 
  published 
  tables 
  com- 
  

   paring 
  pressures 
  found 
  with 
  pressures 
  calculated 
  {he. 
  cit. 
  

   pp. 
  438-440 
  and 
  pp. 
  442-445), 
  and 
  from 
  these 
  it 
  is 
  seen 
  that 
  

   they 
  were 
  willing 
  to 
  allow 
  over 
  1 
  per 
  cent, 
  as 
  a 
  possible 
  

   experimental 
  error. 
  In 
  this 
  connexion 
  they 
  remark 
  : 
  " 
  It 
  is 
  

   to 
  be 
  noticed 
  that 
  the 
  greatest 
  divergence 
  is 
  at 
  the 
  temperatures 
  

   250° 
  and 
  280°, 
  but 
  the 
  deviations 
  are 
  in 
  opposite 
  directions 
  

   and 
  must 
  therefore 
  be 
  ascribed 
  to 
  experimental 
  error 
  " 
  (loc. 
  

   cit. 
  p. 
  444) 
  . 
  

  

  1 
  likewise 
  found 
  in 
  testing 
  my 
  formula 
  that 
  the 
  greatest 
  

   divergence 
  is 
  at 
  temperatures 
  280 
  o, 
  35 
  C. 
  and 
  250° 
  C, 
  and 
  

   that 
  the 
  deviations 
  are 
  .in 
  opposite 
  directions, 
  and 
  therefore 
  

   consider 
  it 
  justifiable 
  to 
  attribute 
  them 
  mainly 
  to 
  the 
  same 
  

   cause. 
  For 
  the 
  remaining 
  temperatures 
  discrepancies 
  occur 
  

   fairly 
  often 
  of 
  over 
  1 
  per 
  cent., 
  but 
  none 
  so 
  great 
  as 
  2 
  per 
  cent., 
  

   so 
  that 
  they 
  still 
  seem 
  to 
  lie 
  within 
  the 
  limits 
  of 
  experimental 
  

   error. 
  

  

  Finally 
  we 
  mny 
  infer 
  that 
  both 
  the 
  general 
  conclusions 
  

   obtained 
  in 
  the 
  former 
  paper 
  with 
  regard 
  to 
  isopentane 
  hold 
  

   good 
  also 
  in 
  the 
  case 
  of 
  ether. 
  

  

  XI. 
  The 
  Wave-Resistance 
  of 
  a 
  Ship. 
  By 
  J. 
  H. 
  Michsll* 
  

  

  T*HE 
  object 
  of 
  this 
  paper 
  is 
  to 
  give 
  a 
  general 
  solution 
  of 
  the 
  

   problem 
  of 
  the 
  waves 
  produced 
  by 
  a 
  ship 
  of 
  given 
  form 
  

   moving 
  with 
  uniform 
  velocity 
  in 
  an 
  inviscid 
  liquid, 
  and 
  to 
  

   determine 
  the 
  consequent 
  wave-resistance 
  to 
  the 
  motion 
  of 
  the 
  

   ship. 
  The 
  only 
  assumption 
  made 
  as 
  to 
  the 
  form 
  of 
  the 
  ship 
  is 
  

   that 
  the 
  inclination 
  of 
  the 
  tangent 
  plane 
  at 
  any 
  point 
  of 
  its 
  

   surface 
  to 
  the 
  vertical 
  median 
  plane 
  is 
  small. 
  This 
  condition 
  

   is 
  not 
  satisfied 
  near 
  the 
  bottom 
  of 
  the 
  middle 
  body 
  of 
  a 
  

   modern 
  ship, 
  but 
  it 
  seems 
  probable 
  that 
  this 
  will 
  not 
  much 
  

   affect 
  either 
  the 
  waves 
  produced 
  or 
  the 
  resistance, 
  for 
  the 
  

   waves 
  arise 
  rather 
  from 
  the 
  parts 
  at 
  the 
  bow 
  and 
  stern 
  at 
  

   which 
  the 
  tangent 
  to 
  the 
  surface 
  is 
  inclined 
  to 
  the 
  direction 
  

   of 
  the 
  ship's 
  motion, 
  than 
  from 
  the 
  approximately 
  cylindrical 
  

   * 
  Communicated 
  by 
  the 
  Author. 
  

  

  