﻿the 
  Viscosity 
  of 
  Glacier 
  Ice. 
  03 
  

  

  effect, 
  and 
  they 
  may 
  reasonably 
  be 
  considered 
  as 
  of 
  infinite 
  

   width. 
  F 
  e 
  is 
  the 
  factor 
  for 
  an 
  ellipse. 
  

  

  In 
  the 
  case 
  of 
  the 
  Hintereis 
  Glacier 
  the 
  stream 
  is 
  com- 
  

   paratively 
  deep 
  as 
  compared 
  with 
  the 
  width, 
  and 
  the 
  form 
  of 
  

   section 
  departs 
  markedly 
  from 
  that 
  of 
  an 
  ellipse. 
  Weinberg's 
  

   method 
  of 
  calculating 
  the 
  viscosity 
  of 
  the 
  Hintereis 
  Glacier 
  

   was 
  to 
  find 
  an 
  ellipse 
  which 
  is 
  the 
  equivalent 
  of 
  the 
  glacier 
  

   bed. 
  

  

  From 
  the 
  dimensions 
  of 
  the 
  semi-axes 
  of 
  his 
  ellipse, 
  

   Weinberg 
  would 
  appear 
  to 
  have 
  used 
  the 
  sections 
  as 
  given 
  

   by 
  Bliimoke 
  and 
  Hess 
  ; 
  but 
  although 
  he 
  states 
  the 
  dimensions 
  

   of 
  the 
  ellipse 
  selected 
  he 
  does 
  not 
  give 
  full 
  details 
  concerning 
  

   the 
  reasons 
  for 
  his 
  selection. 
  

  

  Fig. 
  2 
  (PL 
  III.), 
  upper 
  section, 
  shows 
  the 
  glacier 
  section 
  as 
  

   drawn 
  by 
  Blumcke 
  and 
  Hess*, 
  for 
  their 
  section 
  line 
  V. 
  it 
  

   also 
  shows 
  Weinberg's 
  ellipse 
  for 
  comparison. 
  It 
  will 
  be 
  

   seen 
  that, 
  the 
  ellipse 
  has 
  about 
  the 
  same 
  sectional 
  area 
  as 
  that 
  

   of 
  the 
  actual 
  section. 
  

  

  In 
  fig. 
  2 
  the 
  upper 
  section 
  is 
  the 
  actual 
  section 
  V. 
  given 
  by 
  

   Blumcke 
  and 
  Hess, 
  with 
  the 
  positions 
  of 
  the 
  borings 
  and 
  

   their 
  depths 
  in 
  metres. 
  The 
  lower 
  section 
  gives 
  the 
  glacier 
  

   section 
  distorted 
  so 
  as 
  to 
  bring 
  the 
  upper 
  surface 
  of 
  the 
  

   glacier 
  level. 
  It 
  is 
  more 
  convenient 
  to 
  deal 
  with 
  the 
  section 
  

   in 
  this 
  form, 
  and 
  the 
  slight 
  distortion 
  does 
  not 
  introduce 
  any 
  

   considerable 
  error. 
  In 
  the 
  lower 
  section 
  the 
  curve 
  bb 
  show 
  r 
  s 
  

   the 
  ellipse 
  as 
  fitted 
  to 
  the 
  section 
  by 
  Weinberg, 
  whilst 
  the 
  

   curve 
  aaa 
  shows 
  the 
  glacier 
  section 
  (distorted) 
  of 
  Blumcke 
  

   and 
  Hess. 
  

  

  Although 
  Blumcke 
  and 
  Hess 
  give 
  nine 
  sections 
  across 
  the 
  

   glacier, 
  and 
  all 
  these 
  sections 
  were 
  used 
  by 
  Weinberg 
  for 
  

   calculating 
  the 
  viscosity, 
  only 
  one 
  of 
  these 
  sections 
  is 
  actually 
  

   based 
  upon 
  borings 
  made 
  through 
  the 
  glacier. 
  All 
  the 
  

   borings 
  in 
  the 
  upper 
  section 
  fig. 
  2 
  are 
  considered 
  to 
  have 
  

   touched 
  the 
  bottom. 
  In 
  some 
  cases 
  other 
  borings 
  had 
  to 
  be 
  

   abandoned 
  as 
  they 
  had 
  clearly 
  struck 
  boulders 
  in 
  the 
  ice. 
  

  

  Velocity 
  of 
  Glacier 
  Flow. 
  — 
  The 
  velocity 
  lines 
  given 
  by 
  

   Bliimcke 
  and 
  Hess 
  for 
  the 
  Hintereis 
  Glacier, 
  map 
  fig. 
  3, 
  

   are 
  drawn 
  in 
  metres 
  per 
  annum. 
  During 
  the 
  summer, 
  how- 
  

   ever, 
  the 
  glacier 
  moves 
  faster 
  than 
  it 
  does 
  during 
  the 
  winter. 
  

   This 
  can 
  scarcely 
  be 
  due 
  to 
  the 
  glacier 
  having 
  a 
  higher 
  

   temperature 
  during 
  the 
  summer 
  than 
  during 
  the 
  winter. 
  

   Weinberg 
  suggests 
  that 
  during 
  the 
  summer 
  the 
  sun's 
  heat 
  

   penetrates 
  the 
  ice, 
  and 
  water 
  is 
  formed 
  in 
  its 
  mass. 
  The 
  ice 
  

   is 
  thus 
  weakened 
  and 
  the 
  viscosity 
  of 
  the 
  upper 
  portion- 
  is 
  

   decreased. 
  

  

  * 
  BnH. 
  

  

  