﻿104 
  Messrs. 
  E. 
  M. 
  Deeley 
  and 
  P. 
  H. 
  Parr 
  on 
  

  

  For 
  the 
  viscosity 
  of 
  the 
  Hintereis 
  Glacier 
  we 
  therefore 
  

   have 
  

  

  P 
  = 
  bodily 
  force 
  producing 
  motion, 
  being 
  downward 
  

   component 
  of 
  gravity, 
  

  

  = 
  gravity 
  X 
  density 
  x 
  gradient, 
  

  

  = 
  WXMXI 
  =79 
  . 
  46 
  (13) 
  

  

  The 
  value 
  of 
  F 
  e 
  for 
  the 
  shallow 
  ellipse 
  used 
  by 
  Weinberg 
  

   is 
  0"821, 
  and 
  that 
  for 
  the 
  deeper 
  ellipse 
  we 
  have 
  used 
  

   0*725. 
  The 
  viscosities 
  in 
  the 
  two 
  cases 
  would 
  be 
  proportional 
  

   to 
  156 
  3 
  X 
  0-821 
  and 
  179 
  2 
  x0'651, 
  or 
  to 
  19,779 
  and 
  23,229 
  

   respectively. 
  This 
  shows 
  that 
  the 
  deeper 
  section, 
  although 
  

   of 
  the 
  same 
  area 
  as 
  the 
  actual 
  section, 
  gives 
  the 
  greater 
  

   viscosity. 
  

  

  To 
  obtain 
  the 
  most 
  accurate 
  value 
  for 
  F, 
  the 
  better 
  plan 
  is 
  

  

  to 
  obtain 
  the 
  -^ 
  mean 
  radial 
  value 
  Fe 
  for 
  the 
  deep 
  ellipse 
  

  

  and 
  ascertain 
  the 
  extent 
  to 
  which 
  it 
  differs 
  from 
  the 
  —s 
  mean 
  

  

  y 
  

   radial 
  value 
  F 
  a 
  for 
  the 
  actual 
  section. 
  F 
  e 
  can 
  then 
  be 
  cor- 
  

   rected 
  in 
  this 
  proportion. 
  This 
  would 
  be 
  a 
  more 
  satisfactory 
  

   method 
  if 
  the 
  ellipse 
  agreed 
  more 
  nearly 
  in 
  form 
  with 
  the 
  

   actual 
  glacier 
  section. 
  We 
  thus 
  have 
  

  

  ■F.X*; 
  =0-725x^1 
  

  

  = 
  0-7588. 
  .....: 
  (16) 
  

  

  Using 
  this 
  value 
  of 
  F 
  for 
  the 
  deep 
  section, 
  

  

  « 
  = 
  2 
  79 
  x 
  o^oLT 
  • 
  °- 
  7588 
  - 
  14W 
  * 
  1018 
  - 
  • 
  < 
  l7 
  > 
  

  

  F 
  a 
  and 
  Fe 
  are 
  both 
  somewhat 
  in 
  error, 
  but 
  their 
  ratio 
  is 
  

   probably 
  fairly 
  near 
  to 
  the 
  truth 
  ; 
  therefore, 
  knowing 
  the 
  

  

  p 
  2 
  . 
  F 
  

  

  true 
  value 
  of 
  F 
  e 
  from 
  -£—+ 
  , 
  we 
  have 
  used 
  the 
  ratio 
  ~ 
  as 
  

  

  P 
  + 
  1 
  J? 
  e 
  

  

  a 
  means 
  of 
  deducing 
  the 
  probably 
  correct 
  value 
  of 
  F 
  for 
  the 
  

   deep 
  ellipse 
  fitted 
  to 
  the 
  actual 
  section 
  of 
  the 
  Hintereis 
  

   Glacier. 
  

  

  Although 
  it 
  is 
  possible 
  to 
  use 
  the 
  above 
  formulse 
  for 
  

   calculating 
  the 
  viscosity, 
  the 
  flux 
  cannot 
  be 
  accurately 
  

   obtained 
  from 
  the 
  figures 
  ; 
  for 
  all 
  ellipses 
  of 
  equal 
  area 
  to 
  

   that 
  of 
  the 
  section 
  will 
  not 
  pass 
  the 
  same 
  volume 
  of 
  ice 
  that 
  

   the 
  actual 
  section 
  will. 
  Weinberg's 
  ellipse, 
  for 
  example, 
  is 
  

  

  