﻿T. 
  C. 
  Chamberlin 
  — 
  Mathematics 
  of 
  Isostasy. 
  317 
  

  

  conference 
  named, 
  I 
  briefly 
  expressed 
  my 
  personal 
  view 
  

   that 
  isostasy 
  is 
  accomplished 
  by 
  segmental 
  action 
  in 
  the 
  

   form 
  of 
  wedging, 
  rotation, 
  sliding 
  and 
  like 
  adjustments, 
  

   including 
  internal 
  deformations, 
  consistent 
  with 
  a 
  solid 
  

   earth, 
  rather 
  than 
  by 
  undertow 
  and 
  similar 
  methods 
  

   suitable 
  to 
  a 
  crust 
  floating 
  on 
  a 
  mobile 
  substratum. 
  This 
  

   view 
  of 
  mine 
  stands 
  quite 
  apart 
  from 
  that 
  commonly 
  

   entertained 
  and 
  will 
  require 
  much 
  study 
  in 
  concrete 
  

   detail 
  before 
  it 
  can 
  become 
  a 
  deployed 
  working 
  hypo- 
  

   thesis. 
  Still 
  the 
  very 
  suggestion 
  that 
  such 
  a 
  mode 
  of 
  

   isostatic 
  adjustment 
  is 
  possible, 
  helps 
  to 
  loosen 
  the 
  re- 
  

   straint 
  laid 
  on 
  inquiry 
  by 
  the 
  assumption 
  that 
  there 
  is 
  

   only 
  one 
  method 
  of 
  such 
  adjustment. 
  It 
  should 
  help 
  to 
  

   give 
  inquiry 
  a 
  wholesome 
  freedom. 
  

  

  Note 
  by 
  Charles 
  Schuchert. 
  

  

  As 
  Professor 
  Barrell's 
  literary 
  legatee, 
  it 
  is 
  my 
  duty 
  to 
  say, 
  

   in 
  connection 
  with 
  this 
  discussion, 
  that 
  in 
  Professor 
  MacMillan 
  's 
  

   original 
  article 
  there 
  was 
  not 
  the 
  slightest 
  hint 
  as 
  to 
  the 
  long 
  

   preparation 
  behind 
  the 
  paper, 
  now 
  made 
  so 
  clear 
  by 
  Professor 
  

   Chamberlin. 
  On 
  the 
  other 
  hand, 
  it 
  was 
  MacMillan 
  's 
  first 
  paper 
  

   on 
  isostasy 
  — 
  in 
  fact, 
  the 
  title 
  is 
  "On 
  the 
  Hypothesis 
  of 
  Isos- 
  

   tasy," 
  whereas 
  it 
  is 
  in 
  reality 
  on 
  the 
  use 
  of 
  mathematics 
  in 
  

   isostasy. 
  It 
  should 
  be 
  borne 
  in 
  mind 
  that 
  Barrell 
  was 
  looking 
  

   upon 
  isostasy 
  from 
  the 
  geological 
  side, 
  and 
  that 
  to 
  him 
  mathe- 
  

   matics 
  was 
  but 
  a 
  help 
  in 
  explaining 
  certain 
  features 
  of 
  the 
  

   hypothesis. 
  I 
  doubt 
  very 
  much 
  if 
  he 
  could 
  have 
  taken 
  MacMil- 
  

   lan's 
  view 
  of 
  1917, 
  now 
  made 
  clearer, 
  that 
  is, 
  that 
  "from 
  a 
  

   purely 
  mathematical 
  point 
  of 
  view, 
  any 
  set 
  of 
  a 
  finite 
  number 
  

   of 
  observations 
  of 
  the 
  intensity 
  and 
  direction 
  of 
  gravity 
  can 
  be 
  

   satisfied, 
  not 
  approximately, 
  but 
  exactly, 
  in 
  infinitely 
  many 
  

   ways 
  by 
  a 
  proper 
  distribution 
  of 
  density 
  in 
  the 
  earth." 
  Barrell 
  

   undoubtedly 
  believed 
  that 
  isostasy 
  is 
  primarily 
  a 
  geodetic 
  and 
  

   geologic 
  hypothesis 
  and 
  that 
  it 
  could 
  not 
  be 
  looked 
  upon 
  "from 
  

   a 
  purely 
  mathematical 
  point 
  of 
  view." 
  His 
  viewpoint 
  was 
  that 
  

   of 
  the 
  geologist, 
  and, 
  therefore, 
  very 
  different 
  from 
  that 
  of 
  

   MacMillan. 
  On 
  the 
  other 
  hand, 
  if 
  he 
  had 
  known 
  all 
  that 
  Pro- 
  

   fessor 
  Chamberlin 
  now 
  states 
  of 
  that 
  "memorable 
  discussion," 
  

   and 
  that 
  in 
  the 
  MacMillan 
  article 
  ' 
  ' 
  there 
  was 
  no 
  thought 
  that 
  it 
  

   had 
  any 
  special 
  bearing 
  on 
  any 
  particular 
  discussion 
  of 
  isos- 
  

   tasy, 
  ' 
  ' 
  and 
  the 
  further 
  fact 
  that 
  Chamberlin 
  does 
  not 
  believe 
  in 
  

   a 
  deep-seated 
  zone 
  of 
  special 
  isostatic 
  compensation, 
  undoubtedly 
  

   Barrell 
  would 
  have 
  treated 
  MacMillan's 
  paper 
  very 
  differently. 
  

   I 
  still 
  feel, 
  however, 
  that 
  even 
  in 
  that 
  event 
  he 
  would 
  have 
  taken 
  

   issue 
  with 
  Chamberlin. 
  The 
  crux 
  of 
  the 
  whole 
  affair 
  is 
  that 
  

   there 
  have 
  come 
  to 
  be 
  two 
  explanations 
  of 
  isostasy, 
  one 
  (the 
  

  

  