﻿90 
  Messrs. 
  P. 
  M. 
  Deeley 
  and 
  P. 
  H. 
  Parr 
  on 
  

  

  are 
  the 
  " 
  glacier 
  grains 
  " 
  (gletscherkorner), 
  which 
  play 
  such 
  

   a 
  large 
  part 
  in 
  glacial 
  literature. 
  " 
  Owing 
  to 
  the 
  structure 
  

   being 
  so 
  complex, 
  we 
  failed 
  to 
  trace 
  any 
  relation 
  between 
  

   the 
  arrangement 
  of 
  the 
  crystals 
  and 
  the 
  rapidity 
  of 
  extension. 
  

   It 
  is 
  true 
  that 
  the 
  most 
  rigid 
  of 
  the 
  three 
  was 
  composed 
  

   of 
  small 
  crystals 
  ; 
  but 
  this 
  was 
  perhaps 
  accidental/' 
  

  

  In 
  addition 
  to 
  glacier 
  ice 
  they 
  made 
  several 
  experiments 
  

   on 
  other 
  kinds 
  of 
  ice. 
  Table 
  I. 
  is 
  slightly 
  altered 
  from 
  the 
  

   table 
  of 
  McConnell 
  and 
  Kidd, 
  given 
  on 
  page 
  338 
  of 
  their 
  

   paper 
  as 
  a 
  summary 
  of 
  their 
  experiments. 
  The 
  last 
  column 
  

   giving 
  the 
  viscosities 
  has 
  been 
  added. 
  The 
  mean 
  of 
  their 
  

   results 
  for 
  glacier 
  ice 
  is 
  

  

  7j 
  = 
  84*5 
  x 
  10 
  12 
  poises. 
  

  

  In 
  1899 
  Bliimcke 
  and 
  Hess 
  * 
  published 
  their 
  paper 
  on 
  the 
  

   Hintereis 
  Glacier. 
  Not 
  only 
  did 
  they 
  observe 
  the 
  velocity 
  

   of 
  the 
  ice 
  along 
  a 
  number 
  of 
  lines 
  drawn 
  across 
  the 
  glacier, 
  

   the 
  rate 
  of 
  ablation, 
  and 
  the 
  altitude 
  of 
  its 
  various 
  parts 
  ; 
  

   but, 
  by 
  the 
  help 
  of 
  borings 
  and 
  aided 
  by 
  certain 
  hypothetical 
  

   considerations, 
  they 
  attempted 
  to 
  construct 
  sections 
  of 
  the 
  

   glacier 
  showing 
  its 
  width 
  and 
  depth 
  at 
  certain 
  positions. 
  

   The 
  methods 
  adopted 
  for 
  drawing 
  the 
  sections 
  are 
  open 
  to 
  

   some 
  objections 
  ; 
  but 
  they 
  appear 
  to 
  have 
  used 
  with 
  skill 
  the 
  

   only 
  methods 
  open 
  to 
  them, 
  and 
  the 
  sections 
  they 
  have 
  thus 
  

   obtained 
  are 
  probably 
  approximately 
  correct. 
  

  

  The 
  method, 
  Bliimcke 
  and 
  Hess 
  state, 
  is 
  a 
  very 
  laborious 
  

   one; 
  for 
  it 
  involves 
  tracing 
  the 
  stream 
  lines 
  in 
  the 
  ice, 
  

   and 
  ascertaining 
  accurately 
  the 
  ablation 
  and 
  surface 
  velocity 
  

   of 
  all 
  points 
  on 
  the 
  glacier 
  tongue. 
  The 
  main 
  objection 
  to 
  

   their 
  method 
  is 
  that 
  they 
  assume, 
  in 
  the 
  first 
  place, 
  that 
  

   the 
  velocity 
  is 
  the 
  same 
  in 
  all 
  vertical 
  lines. 
  This 
  would 
  

   make 
  the 
  glacier 
  too 
  shallow, 
  for 
  the 
  glacier 
  slips 
  bodily 
  

   and 
  also 
  flows 
  differentially. 
  They 
  then 
  ascertained 
  the 
  

   actual 
  thickness 
  at 
  certain 
  points 
  by 
  actual 
  borings 
  

   through 
  the 
  ice, 
  and 
  increased 
  the 
  thickness 
  of 
  the 
  ice 
  

   everywhere 
  in 
  proportion 
  to 
  the 
  extra 
  thickness 
  thus 
  ascer- 
  

   tained. 
  But 
  the 
  velocity 
  at 
  any 
  point 
  on 
  the 
  surface 
  does 
  

   not 
  depend 
  entirely 
  on 
  the 
  thickness 
  of 
  the 
  ice 
  at 
  that 
  place. 
  

   The 
  velocity 
  at 
  any 
  point 
  on 
  the 
  surface 
  is 
  affected 
  by 
  the 
  

   depth 
  of 
  the 
  ice 
  at 
  all 
  points 
  of 
  the 
  section, 
  and 
  to 
  a 
  certain 
  

   extent 
  on 
  the 
  shape 
  of 
  the 
  undersurface 
  of 
  the 
  glacier 
  above 
  

   and 
  below 
  the 
  section. 
  However, 
  the 
  sections 
  are 
  the 
  most 
  

   accurate 
  that 
  have 
  yet 
  been 
  obtained, 
  and 
  great 
  praise 
  is 
  due 
  

   to 
  Bliimcke 
  and 
  Hess 
  for 
  the 
  work 
  they 
  have 
  accomplished. 
  

  

  * 
  Wiss, 
  Erg-Hefte 
  z. 
  Zeitschr. 
  d. 
  D. 
  u. 
  0. 
  A.-V, 
  ii., 
  Munich, 
  1899. 
  

  

  