﻿506 
  

  

  Prof. 
  O. 
  Reynolds 
  on 
  Rolling 
  -Friction, 
  [June 
  17 
  3 
  

  

  and 
  a 
  current, 
  whose 
  intensity, 
  C, 
  was 
  measured 
  by 
  the 
  tangent 
  galva- 
  

   nometer 
  included 
  in 
  the 
  circuit, 
  was 
  sent 
  through 
  the 
  helix 
  first 
  in 
  one 
  

   direction 
  and 
  then 
  in 
  the 
  other, 
  and 
  the 
  plane 
  of 
  polarization 
  observed. 
  

   Half 
  the 
  difference 
  of 
  the 
  readings 
  was 
  the 
  rotation 
  produced 
  by 
  the 
  

   current. 
  

  

  If 
  we 
  call 
  6 
  this 
  rotation 
  expressed 
  in 
  circular 
  measure, 
  and 
  define 
  

   Terdet's 
  constant 
  as 
  the 
  rotation 
  which 
  a 
  unit 
  current 
  in 
  a 
  unit 
  coil 
  

   could 
  produce 
  in 
  unit 
  of 
  length 
  of 
  distilled 
  water, 
  we 
  have 
  

  

  _ 
  6 
  

  

  w 
  1N 
  T 
  C' 
  

  

  The 
  result 
  of 
  the 
  series 
  of 
  experiments 
  made 
  was 
  to 
  obtain 
  for 
  to 
  the 
  

   value 
  

  

  o)= 
  (10~ 
  7 
  )4-49 
  centimetre-gramme-seconds. 
  

  

  Its 
  dimensions 
  obviously 
  are 
  the 
  reciprocal 
  of 
  those 
  of 
  current, 
  viz. 
  

  

  M 
  = 
  [L-iM-IT]. 
  

  

  If 
  we 
  put 
  our 
  result 
  in 
  a 
  slightly 
  different 
  form 
  we 
  may 
  say 
  that, 
  

   If 
  plane 
  polarized 
  light 
  passes 
  through 
  distilled 
  water, 
  and 
  the 
  mag- 
  

   netic 
  potential 
  of 
  the 
  water 
  at 
  any 
  two 
  points 
  in 
  the 
  path 
  of 
  the 
  ray 
  

   differs 
  by 
  unity, 
  then 
  the 
  plane 
  of 
  polarization 
  will 
  be 
  rotated 
  between 
  

   those 
  points 
  4| 
  ten-millionths 
  of 
  a 
  unit 
  of 
  circular 
  measure. 
  

  

  Cavendish 
  Laboratory, 
  Cambridge, 
  

   April 
  30, 
  1875. 
  

  

  V. 
  "On 
  Rolling-Friction." 
  By 
  Professor 
  Osborne 
  Reynolds. 
  

   Communicated 
  by 
  Dr. 
  Balfour 
  Stewart, 
  F.R.S. 
  Received 
  

   May 
  24, 
  1875. 
  

  

  (Abstract.) 
  

  

  The 
  motion 
  of 
  a 
  roller 
  or 
  wheel 
  on 
  a 
  surface 
  is 
  always 
  attended 
  with 
  

   resistance. 
  Coulomb 
  made 
  some 
  experiments 
  with 
  wooden 
  rollers 
  on 
  a 
  

   wooden 
  plane, 
  from 
  which 
  he 
  deduced 
  two 
  laws, 
  viz. 
  that 
  the 
  resistance 
  

   is 
  proportional 
  to 
  the 
  weight 
  of 
  the 
  roller, 
  and 
  inversely 
  proportional 
  to 
  

   its 
  diameter. 
  These 
  laws 
  have 
  since 
  been 
  found 
  to 
  apply 
  to 
  other 
  sub- 
  

   stances, 
  a 
  different 
  coefficient 
  being 
  used 
  in 
  each 
  case. 
  Beyond 
  this, 
  

   however, 
  nothing 
  appears 
  hitherto 
  to 
  have 
  been 
  ascertained 
  as 
  regards 
  

   the 
  nature 
  of 
  this 
  resistance 
  to 
  rolling. 
  The 
  source 
  from 
  which 
  it 
  springs 
  

   does 
  not 
  appear 
  to 
  have 
  been 
  made 
  the 
  subject 
  of 
  investigation. 
  

  

  Some 
  time 
  ago 
  it 
  occurred 
  to 
  the 
  author 
  that 
  it 
  was 
  probable 
  that 
  the 
  

   deformation 
  of 
  the 
  surface 
  of 
  the 
  roller 
  and 
  of 
  the 
  plane, 
  which 
  must 
  

   take 
  place 
  at 
  the 
  point 
  of 
  contact, 
  would 
  affect 
  the 
  distance 
  which 
  the 
  

   roller 
  would 
  advance 
  in 
  turning 
  through 
  a 
  certain 
  angle 
  *. 
  The 
  pressure 
  

   of 
  the 
  roller 
  on 
  the 
  plane 
  causes 
  a 
  certain 
  temporary 
  indentation 
  and 
  

   * 
  The 
  Engineer, 
  27th 
  Nov., 
  1874 
  

  

  