﻿318 
  W. 
  D. 
  MacMillan 
  — 
  Mathematics 
  of 
  Isostasy. 
  

  

  newer 
  one 
  of 
  Chamberlin) 
  regarding 
  it 
  as 
  brought 
  about 
  "by 
  

   segmental 
  action 
  in 
  the 
  form 
  of 
  wedging, 
  rotation, 
  sliding 
  and 
  

   like 
  adjustments, 
  including 
  internal 
  deformations, 
  consistent 
  

   with 
  a 
  solid 
  earth"; 
  the 
  other 
  (of 
  geologists 
  in 
  general 
  and 
  

   Barrell) 
  holding 
  it 
  to 
  be 
  effected 
  "by 
  undertow 
  and 
  similar 
  

   methods 
  suitable 
  to 
  a 
  crust 
  floating 
  on 
  a 
  mobile 
  substratum." 
  

  

  The 
  Mathematics 
  of 
  Isostasy. 
  II 
  ; 
  by 
  William 
  

   D. 
  MacMillast. 
  

  

  My 
  attention 
  has 
  been 
  called 
  to 
  a 
  severe 
  attack 
  in 
  this 
  

   Journal 
  for 
  last 
  October 
  by 
  the 
  late 
  Professor 
  Barrell 
  

   on 
  my 
  paper 
  on 
  Isostasy 
  which 
  was 
  printed 
  in 
  volume 
  

   25 
  of 
  the 
  Journal 
  of 
  Geology. 
  1 
  A 
  somewhat 
  lengthy 
  

   absence 
  from 
  the 
  city 
  and 
  from 
  my 
  usual 
  duties 
  has 
  de- 
  

   layed 
  my 
  reply. 
  

  

  A 
  careful 
  reading 
  of 
  Barrell 
  's 
  paper 
  seems 
  to 
  reveal 
  

   a 
  feeling 
  of 
  irritation 
  which 
  I 
  am 
  sure 
  grew 
  out 
  of 
  a 
  

   misinterpretation 
  of 
  the 
  real 
  purpose 
  and 
  nature 
  of 
  my 
  

   paper. 
  To 
  set 
  the 
  matter 
  right, 
  the 
  first 
  step 
  is 
  to 
  dis- 
  

   cover 
  just 
  where 
  the 
  error 
  of 
  interpretation 
  entered 
  and 
  

   what 
  its 
  correction 
  requires. 
  

  

  As 
  a 
  first 
  point, 
  it 
  is 
  to 
  be 
  noted 
  that 
  my 
  paper 
  was 
  

   written 
  by 
  a 
  mathematician 
  for 
  geologists, 
  but 
  there 
  was 
  

   no 
  misunderstanding 
  about 
  this, 
  for 
  Dr. 
  Barrell 
  himself 
  

   recognizes 
  it 
  on 
  page 
  314. 
  This 
  fact 
  is 
  to 
  be 
  kept 
  in 
  

   mind. 
  

  

  The 
  key 
  to 
  Barrell 
  's 
  misreading 
  of 
  my 
  paper 
  may 
  be 
  

   found, 
  I 
  think, 
  in 
  his 
  opening 
  statement 
  respecting 
  it 
  

   (p. 
  316). 
  In 
  this 
  he 
  says: 
  "Its 
  attitude 
  is 
  that 
  of 
  skep- 
  

   ticism 
  toward 
  any 
  specific 
  form 
  of 
  isostatic 
  theory 
  and 
  

   of 
  destructive 
  criticism 
  toward 
  the 
  one 
  employed 
  by 
  Hay- 
  

   ford." 
  2 
  The 
  real 
  attitude 
  of 
  the 
  paper 
  can 
  be 
  judged 
  

   from 
  the 
  quotations 
  that 
  follow: 
  

  

  My 
  own 
  opening 
  statement 
  is 
  this 
  : 
  

  

  The 
  splendid 
  papers 
  by 
  Hayford 
  and 
  jointly 
  by 
  Hayford 
  and 
  

   Bowie 
  have 
  brought 
  the 
  subject 
  of 
  isostasy 
  into 
  the 
  foreground 
  

   for 
  discussion 
  by 
  geologists 
  and 
  others 
  who 
  may 
  be 
  interested. 
  

   These 
  papers 
  have 
  taken 
  the 
  subject 
  out 
  of 
  a 
  field 
  of 
  more 
  or 
  

   less 
  vague 
  conjecture, 
  and 
  by 
  subjecting 
  it 
  to 
  a 
  very 
  careful 
  

   quantitative 
  examination 
  have 
  shown 
  very 
  clearly 
  that 
  isostasy 
  

   in 
  some 
  form 
  can 
  be 
  accepted 
  as 
  a 
  reality 
  (p. 
  105). 
  

  

  1 
  Jour. 
  Geol., 
  vol. 
  25, 
  Feb.-Mar., 
  p. 
  105, 
  1917. 
  

  

  2 
  This 
  Journal, 
  48, 
  p. 
  316, 
  Oct., 
  1919. 
  

  

  