﻿92 
  Messrs. 
  R. 
  M. 
  Deeley 
  and 
  P. 
  H. 
  Parr 
  on 
  

  

  In 
  the 
  present 
  paper 
  we 
  now 
  purpose 
  discussing 
  the 
  data 
  

   furnished 
  by 
  Bliimcke 
  and 
  Hess, 
  with 
  a 
  view 
  to 
  calculating 
  

   the 
  viscosity 
  of 
  the 
  Hintereis 
  Glacier. 
  Weinberg, 
  as 
  we 
  

   have 
  seen, 
  has 
  already 
  attempted 
  this, 
  but 
  his 
  result, 
  although 
  

   it 
  agrees 
  with 
  his 
  torsion 
  experiment 
  on 
  glacier 
  ice, 
  does 
  not 
  

   agree 
  with 
  the 
  tensile 
  tests 
  of 
  Dr. 
  Main 
  and 
  McConneU 
  and 
  

   Kidd. 
  

  

  The 
  conditions 
  of 
  flow 
  of 
  viscous 
  fluids 
  are 
  only 
  known 
  

   for 
  certain 
  shaped 
  channels. 
  The 
  simplest 
  known 
  conditions 
  

   of 
  flow 
  are 
  along 
  semicircular, 
  elliptic, 
  or 
  channels 
  of 
  great 
  

   width 
  as 
  compared 
  with 
  depth. 
  

  

  The 
  force 
  producing 
  motion 
  in 
  the 
  case 
  of 
  a 
  glacier 
  is 
  

   gravity, 
  and 
  it 
  is 
  measured 
  in 
  dynes 
  per 
  cubic 
  centimetre 
  

   = 
  gravity 
  x 
  density 
  x 
  gradient 
  = 
  P. 
  

  

  For 
  glaciers 
  so 
  wide 
  that 
  they 
  may 
  be 
  considered 
  as 
  of 
  

  

  infinite 
  width, 
  we 
  have 
  

  

  Pb 
  2 
  

   Viscosity 
  v<c 
  = 
  —, 
  (4) 
  

  

  where 
  rj^ 
  is 
  the 
  viscosity 
  without 
  correction 
  for 
  width, 
  b 
  is 
  

   the 
  thickness 
  of 
  the 
  glacier, 
  and 
  V 
  the 
  maximum 
  surface 
  

   velocity, 
  all 
  in 
  C.Gr.S. 
  units. 
  

  

  For 
  semi-elliptic 
  channels 
  the 
  corresponding 
  equation 
  is 
  

  

  Pa 
  2 
  b 
  2 
  r 
  , 
  

  

  7? 
  ~2V(a 
  2 
  +6 
  2 
  )' 
  l 
  ; 
  

  

  a 
  being 
  the 
  semi-width 
  and 
  b 
  the 
  depth, 
  which 
  is 
  equation 
  

   (4) 
  multiplied 
  by 
  

  

  - 
  = 
  F 
  

  

  so 
  that 
  

  

  a 
  2 
  + 
  b 
  

  

  V 
  = 
  V„? 
  (6) 
  

  

  Writing 
  p 
  for 
  the 
  ratio 
  r 
  we 
  have 
  

  

  a 
  = 
  -E 
  -F 
  (7) 
  

  

  a 
  2 
  + 
  6 
  2 
  p 
  2 
  +l 
  K 
  } 
  

  

  It 
  will 
  appear 
  later 
  that 
  the 
  method 
  of 
  considering 
  the 
  

   true 
  viscosity 
  77 
  to 
  be 
  equal 
  to 
  that 
  obtained 
  by 
  considering 
  

   the 
  glacier 
  as 
  of 
  infinite 
  width, 
  77^, 
  multiplied 
  by 
  a 
  f 
  actor 
  F 
  

   depending 
  upon 
  the 
  section 
  of 
  the 
  bed, 
  is 
  convenient 
  in 
  

  

  several 
  respects. 
  As 
  p, 
  or 
  r, 
  increases, 
  F 
  c 
  rapidly 
  approaches 
  

  

  unity, 
  as 
  is 
  clearly 
  shown 
  in 
  fig. 
  1 
  (PL 
  III.), 
  so 
  that 
  for 
  wide 
  

   glaciers 
  of 
  regular 
  thickness 
  the 
  actual 
  width 
  has 
  very 
  little 
  

  

  