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  III. 
  The 
  Viscosity 
  of 
  Glacier 
  Ice. 
  

   B>/ 
  R. 
  M. 
  Deeley, 
  MJnst.C.k, 
  F.G.S., 
  and 
  P. 
  H. 
  Parr*. 
  

  

  [Plate 
  III.] 
  

  

  SEVERAL 
  authors 
  have 
  already 
  dealt 
  with 
  the 
  flow 
  of 
  

   glaciers 
  considered 
  as 
  viscous 
  fluid 
  masses 
  ; 
  but 
  the 
  

   absence 
  of 
  reliable 
  data 
  concerning 
  their 
  thickness 
  and 
  the 
  

   slopes 
  of 
  their 
  surfaces 
  has 
  rendered 
  impossible 
  any 
  exact 
  

   mathematical 
  analysis 
  of 
  their 
  movement. 
  However, 
  during 
  

   recent 
  years 
  a 
  good 
  deal 
  of 
  detailed 
  information 
  has 
  been 
  

   published 
  concerning 
  the 
  dimensions 
  of 
  several 
  glaciers, 
  and 
  

   the 
  velocities 
  with 
  which 
  they 
  move. 
  One 
  of 
  the 
  most 
  

   thorough 
  pieces 
  of 
  work 
  of 
  this 
  description 
  has 
  been 
  carried 
  

   out 
  by 
  Bliimcke 
  and 
  Hess 
  on 
  the 
  Hintereis 
  Glacier, 
  Otztal, 
  

   in 
  the 
  Austrian 
  Alps. 
  

  

  Before 
  discussing 
  the 
  latest 
  data 
  upon 
  which 
  a 
  calculation 
  

   of 
  the 
  viscosity 
  of 
  glacier 
  ice 
  can 
  be 
  based, 
  we 
  will 
  give 
  in 
  

   outline 
  the 
  work 
  on 
  this 
  subject 
  which 
  has 
  been 
  done 
  up 
  to 
  

   date. 
  

  

  In 
  1888 
  Dr. 
  Main 
  f 
  published 
  the 
  results 
  of 
  some 
  experi- 
  

   ments 
  made 
  in 
  the 
  winter 
  of 
  1886-7 
  on 
  the 
  yielding 
  to 
  

   tension, 
  at 
  several 
  degrees 
  below 
  the 
  freezing-point, 
  of 
  bars 
  

   of 
  ice 
  formed 
  by 
  freezing 
  water 
  in 
  an 
  iron 
  mould. 
  Tyndall 
  

   had 
  previously 
  contended 
  that 
  glacier 
  ice 
  would 
  not 
  yield 
  to 
  

   tension 
  and 
  was 
  not, 
  therefore, 
  to 
  be 
  considered 
  as 
  a 
  viscous 
  

   substance. 
  Main's 
  experimental 
  results, 
  however, 
  disposed 
  of 
  

   this 
  objection. 
  

  

  In 
  a 
  paper 
  published 
  in 
  1888, 
  Kelvin 
  \ 
  calculated 
  from 
  

   the 
  data 
  furnished 
  by 
  Main's 
  experiments 
  the 
  viscosity 
  of 
  

   the 
  ice 
  used 
  by 
  Main, 
  and 
  thereby 
  arrived 
  at 
  some 
  definite 
  

   conclusions 
  concerning 
  the 
  probable 
  thickness 
  of 
  ice 
  sheets 
  

   and 
  glaciers 
  under 
  certain 
  conditions. 
  He, 
  however, 
  did 
  not 
  

   publish 
  the 
  figure 
  obtained 
  by 
  him 
  for 
  the 
  viscosity. 
  

  

  In 
  1888 
  McConnell 
  and 
  Kidd 
  § 
  published 
  the 
  results 
  of 
  

   some 
  experiments 
  on 
  the 
  yielding 
  of 
  various 
  kinds 
  of 
  ice 
  to 
  

   tension 
  and 
  compression. 
  These 
  experiments 
  were 
  made 
  

   partly 
  with 
  the 
  apparatus 
  used 
  by 
  Dr. 
  Main. 
  

  

  In 
  1888 
  A. 
  Odin 
  [| 
  endeavoured 
  to 
  construct 
  equations 
  

  

  * 
  Communicated 
  bv 
  the 
  Authors. 
  

  

  t 
  Proc. 
  Roy. 
  Soc. 
  vol. 
  xlii. 
  (1907). 
  

  

  X 
  ' 
  Popular 
  Lectures 
  and 
  Addresses,' 
  vol. 
  ii. 
  pp. 
  319-359. 
  

  

  § 
  Proc. 
  Roy. 
  Soc. 
  vol. 
  xliv. 
  pp. 
  331-367. 
  

  

  II 
  A. 
  Odin, 
  *' 
  Essai 
  d'un 
  application 
  des 
  princip^s 
  de 
  la 
  mechaiiique 
  

   a 
  1'tScoulement 
  des 
  glaciers." 
  Bull. 
  Soc. 
  oaud. 
  d. 
  sc. 
  nut. 
  (3) 
  Vul. 
  xxiv. 
  

   p. 
  33 
  (1868.) 
  

  

  