﻿954 
  Prof. 
  A. 
  H. 
  Gibson 
  on 
  tlie 
  Motion 
  of 
  

  

  ranged 
  from 
  9° 
  C. 
  to 
  11° 
  C. 
  At 
  the 
  mean 
  temperature 
  

   of 
  10° 
  C, 
  the 
  coefficient 
  of 
  viscosity 
  fi, 
  calculated 
  from 
  

   Poiseuille's 
  formula 
  

  

  _ 
  -0000181 
  

  

  fJ 
  '~ 
  1 
  + 
  -03368 
  1 
  + 
  -00021* 
  2 
  ' 
  

  

  is 
  '00001333 
  grammes 
  wt. 
  per 
  sq. 
  cm., 
  while 
  the 
  value 
  of 
  the 
  

   surface-tension 
  T 
  at 
  the 
  boundary 
  surface 
  of 
  air 
  and 
  water, 
  

   as 
  calculated 
  from 
  the 
  relationship 
  

  

  T=-0752(l--00187*), 
  

  

  = 
  '0738 
  grammes 
  per 
  centimetre. 
  

  

  These 
  values 
  of 
  /jl 
  and 
  of 
  T 
  have 
  been 
  used 
  throughout 
  the 
  

   calculations. 
  

  

  3. 
  Velocity 
  of 
  Long 
  Bubbles. 
  — 
  The 
  experiments 
  showed 
  the 
  

   somewhat 
  unexpected 
  result 
  that 
  if 
  the 
  bubble 
  is 
  so 
  long 
  as 
  

   to 
  adopt 
  a 
  cylindrical 
  form, 
  i. 
  e. 
  for 
  lengths 
  greater 
  than 
  the 
  

   bore 
  of 
  the 
  tube, 
  the 
  mean 
  velocity 
  is 
  sensibly 
  independent 
  

   of 
  the 
  length 
  within 
  the 
  limits 
  of 
  length 
  (up 
  to 
  about 
  20 
  

   diameters 
  in 
  the 
  smaller 
  tubes) 
  investigated. 
  The 
  mean 
  

   results 
  of 
  these 
  experiments 
  are 
  as 
  follows 
  : 
  — 
  

  

  Table 
  I. 
  

   Velos. 
  — 
  cm. 
  per 
  sec. 
  

  

  1 
  

  

  Length 
  of 
  bubble 
  in 
  terms 
  of 
  bore 
  o 
  

  

  f 
  tube. 
  

  

  

  Diam. 
  of 
  tube, 
  

   cm. 
  

  

  

  

  Mean 
  

   velocity. 
  

  

  

  

  

  

  

  

  •420 
  

  

  1. 
  

  

  2. 
  

  

  3. 
  

  

  5. 
  

  

  10. 
  

  

  20. 
  

  

  

  

  

  Bubb 
  

  

  le 
  stat 
  

  

  ionary 
  

  

  

  

  •536 
  

  

  

  •0276 
  

  

  •0277 
  

  

  •0281 
  

  

  •0277 
  

  

  

  •0278 
  

  

  •560 
  

  

  3 
  V 
  36 
  

  

  3-36 
  

  

  3-35 
  

  

  3-36 
  

  

  

  

  3-36 
  

  

  •788 
  

  

  333 
  

  

  3-23 
  

  

  3-23 
  

  

  321 
  

  

  321 
  

  

  3-19 
  

  

  323 
  

  

  1-321 
  

  

  10-2 
  

  

  10-3 
  

  

  10-3 
  

  

  10-3 
  

  

  10-3 
  

  

  10-3 
  

  

  10-3 
  

  

  1-680 
  

  

  150 
  

  

  15-0 
  

  

  15-0 
  

  

  150 
  

  

  150 
  

  

  151 
  

  

  150 
  

  

  1-796 
  

  

  161 
  

  

  16-3 
  

  

  16-3 
  

  

  163 
  

  

  16-4 
  

  

  

  16-3 
  

  

  2-695 
  

  

  234 
  

  

  23-4 
  

  

  23-4 
  

  

  233 
  

  

  

  

  23-4 
  

  

  509 
  

  

  299 
  

  

  29-9 
  

  

  

  

  

  

  29-9 
  

  

  7-78 
  

  

  32-9 
  

  

  329 
  

  

  

  ... 
  

  

  I 
  

  

  

  

  32-9 
  

  

  After 
  trying 
  various 
  systems 
  of 
  plotting, 
  it 
  was 
  found 
  that 
  

   these 
  results 
  are 
  very 
  nearly 
  represented 
  by 
  the 
  relationship 
  

  

  34-6- 
  

  

  114-0 
  

  

  cm. 
  sec. 
  

  

  d 
  2 
  + 
  3-012 
  

   where 
  d 
  is 
  the 
  diameter 
  of 
  the 
  tube 
  in 
  cm. 
  

  

  (i) 
  

  

  