﻿the 
  Viscosity 
  of 
  Glacier 
  Ice. 
  105 
  

  

  too 
  shallow. 
  The 
  additional 
  area 
  ohtained 
  at 
  the 
  sides 
  does 
  

   not 
  compensate 
  for 
  the 
  absence 
  of 
  the 
  deep 
  channel 
  near 
  the 
  

   centre. 
  The 
  deeper 
  section 
  we 
  have 
  fitted 
  gives 
  a 
  more 
  

   accurate 
  result. 
  

  

  So 
  far 
  we 
  have 
  not 
  succeeded 
  in 
  devising 
  a 
  method 
  on 
  

  

  similar 
  lines 
  to 
  the 
  -3 
  radial 
  method, 
  for 
  fitting 
  an 
  ellipse 
  to 
  

  

  the 
  section 
  which 
  will 
  give 
  a 
  channel 
  of 
  equal 
  area 
  to 
  the 
  

   actual 
  one, 
  and 
  at 
  the 
  same 
  time 
  one 
  that 
  will 
  pass 
  an 
  equal 
  

   volume 
  of 
  ice. 
  

  

  The 
  most 
  reasonable 
  method 
  is 
  to 
  use 
  formula 
  (17). 
  

  

  it 
  x 
  79-46 
  x 
  29100 
  3 
  x 
  17900 
  3 
  _ 
  

   8xt?x(29100 
  2 
  + 
  17900 
  2 
  ) 
  ~ 
  

  

  In 
  addition 
  to 
  the 
  flux 
  due 
  to 
  differential 
  flow 
  the 
  volume 
  

   which 
  moves 
  down 
  owing 
  to 
  the 
  bodily 
  slip 
  of 
  the 
  glacier 
  

   must 
  also 
  be 
  added. 
  This, 
  for 
  the 
  winter 
  flow, 
  can 
  be 
  

   approximately 
  calculated 
  as 
  follows 
  : 
  

  

  B 
  ,., 
  n 
  22100 
  x 
  17900 
  x 
  3-1416 
  xYj 
  /10 
  , 
  

  

  bodily 
  nux 
  = 
  -. 
  . 
  (18) 
  

  

  Here 
  V 
  x 
  is 
  the 
  mean 
  velocity. 
  This 
  can 
  only 
  be 
  obtained 
  

   approximately, 
  as 
  the 
  exact 
  variation 
  of 
  the 
  velocity 
  from 
  the 
  

   centre 
  to 
  the 
  sides 
  is 
  not 
  known. 
  

  

  For 
  the 
  summer 
  flux, 
  the 
  additional 
  volume 
  passed 
  owing 
  

   to 
  the 
  lower 
  viscosity 
  of 
  the 
  surface 
  portions 
  of 
  the 
  ice 
  must 
  

   be 
  added. 
  This 
  quantity 
  is 
  also 
  uncertain, 
  but 
  it 
  forms 
  only 
  

   a 
  small 
  portion 
  of 
  the 
  total 
  flux. 
  

  

  Although 
  for 
  the 
  calculation 
  of 
  the 
  viscosity 
  an 
  ellipse 
  

   gives 
  fairly 
  satisfactory 
  results, 
  this 
  form 
  of 
  curve 
  does 
  not 
  

   fit 
  an 
  actual 
  glaciated 
  valley 
  at 
  all 
  satisfactorily. 
  On 
  this 
  

   account 
  the 
  speed 
  curve 
  given 
  by 
  an 
  ellipse 
  varies 
  very 
  

   greatly 
  from 
  that 
  of 
  the 
  surface-velocity 
  curve 
  of 
  a 
  glacier. 
  

   We 
  have, 
  therefore, 
  attempted 
  to 
  discover 
  a 
  form 
  of 
  curve 
  

   which 
  agrees 
  more 
  closely 
  with 
  the 
  section 
  of 
  a 
  glaciated 
  

   valley. 
  Although 
  such 
  a 
  curve 
  has 
  been 
  found, 
  and 
  is 
  

   described 
  in 
  the 
  Appendix 
  to 
  this 
  paper, 
  the 
  rather 
  abnormal 
  

   form 
  of 
  the 
  section 
  of 
  the 
  Hintereis 
  Glacier 
  renders 
  it, 
  for 
  

   our 
  present 
  purpose, 
  not 
  quite 
  so 
  useful 
  as 
  it 
  may 
  be 
  

   in 
  other 
  cases. 
  AVe 
  might 
  here 
  suggest 
  the 
  advisability 
  of 
  

   making 
  another 
  boring 
  through 
  the 
  glacier, 
  on 
  section 
  V., 
  

   near 
  the 
  one 
  which 
  shows 
  a 
  thickness 
  of 
  163 
  metres. 
  If 
  

   this 
  boring 
  should 
  thus 
  be 
  proved 
  to 
  have 
  struck 
  a 
  stone 
  and 
  

   not 
  reached 
  the 
  bottom, 
  the 
  surface-velocity 
  curve 
  may 
  not 
  

   be 
  quite 
  as 
  abnormal 
  as 
  it 
  now 
  appears 
  to 
  be. 
  

  

  