﻿AGE 
  OF 
  THE 
  EAETH 
  — 
  CHAMBEKLIN 
  AND 
  OTHERS. 
  253 
  

  

  put 
  in 
  definite 
  form 
  by 
  Leith 
  and 
  Mead. 
  16 
  Comparing 
  first 
  the 
  

   igneous 
  rocks 
  with 
  the 
  sediments, 
  they 
  find 
  the 
  following 
  excesses 
  

   and 
  deficiencies: 
  (1) 
  a 
  deficiency 
  of 
  3.1 
  per 
  cent 
  in 
  iron; 
  (2) 
  a 
  de- 
  

   ficiency 
  of 
  26 
  per 
  cent 
  in 
  magnesium; 
  (3) 
  an 
  excess 
  of 
  32 
  per 
  cent 
  in 
  

   calcium; 
  (4) 
  a 
  deficiency 
  of 
  64 
  per 
  cent 
  in 
  sodium; 
  and 
  (5) 
  an 
  excess 
  

   of 
  2 
  per 
  cent 
  in 
  potassium. 
  If 
  the 
  corresponding 
  constituents 
  in 
  the 
  

   ocean 
  are 
  added 
  to 
  these 
  severally, 
  some 
  of 
  the 
  discrepancies 
  will 
  be 
  

   lessened, 
  while 
  others 
  will 
  be 
  increased; 
  the 
  discrepancies 
  do 
  not 
  

   disappear, 
  though 
  they 
  are 
  somewhat 
  mitigated. 
  

  

  2. 
  It 
  is 
  recognized 
  on 
  all 
  hands 
  that 
  the 
  land 
  waters 
  vary 
  greatly 
  

   according 
  to 
  the 
  nature 
  of 
  the 
  drainage 
  area 
  from 
  which 
  they 
  are 
  

   derived. 
  In 
  some 
  districts 
  they 
  consist 
  largely 
  of 
  carbonates, 
  or 
  of 
  

   sulphates 
  ; 
  in 
  others 
  of 
  chlorides, 
  or 
  of 
  silicates 
  ; 
  while 
  the 
  degree 
  of 
  

   dominance 
  varies 
  greatly 
  within 
  each 
  class. 
  The 
  solutions 
  of 
  the 
  

   ocean, 
  however, 
  are 
  not 
  identical 
  with 
  any 
  of 
  these, 
  nor 
  with 
  a 
  simple 
  

   mixture 
  of 
  them; 
  the 
  ocean 
  solutions 
  are 
  dominantly 
  chlorides, 
  but 
  

   constitute 
  a 
  combination 
  which 
  is 
  quite 
  distinctive. 
  This 
  implies 
  that, 
  

   instead 
  of 
  a 
  theoretical 
  mixture 
  of 
  the 
  land 
  waters, 
  an 
  effective 
  

   «.hemico-physical 
  reorganization 
  takes 
  place, 
  a 
  liquid 
  metamorphism 
  

   of 
  the 
  heterogeneous 
  land 
  waters 
  and 
  their 
  content 
  into 
  the 
  homo- 
  

   geneous 
  sea 
  solution 
  and 
  its 
  sediments. 
  This 
  is 
  in 
  a 
  measure 
  recog- 
  

   nized, 
  but 
  the 
  recognition 
  is 
  inadequate 
  if 
  the 
  change 
  is 
  regarded 
  

   simply 
  as 
  a 
  liquid 
  metamorphism. 
  There 
  is 
  a 
  neglected 
  solid 
  factor 
  

   in 
  the 
  form 
  of 
  silts 
  and 
  clays 
  that 
  is 
  of 
  critical 
  importance. 
  The 
  

   usual 
  comparison 
  is 
  really 
  between 
  the 
  clear 
  waters 
  of 
  the 
  streams 
  — 
  

   which 
  are 
  mainly 
  the 
  outflowing 
  ground 
  waters 
  of 
  the 
  land 
  — 
  and 
  the 
  

   sea 
  waters. 
  The 
  run-off 
  and 
  its 
  contents 
  — 
  the 
  wash-waters 
  of 
  the 
  

   land 
  and 
  their 
  burden 
  of 
  mud 
  — 
  are 
  neglected. 
  But 
  it 
  is 
  this 
  run-off 
  

   water 
  with 
  its 
  mud 
  and 
  the 
  colloids 
  that 
  go 
  with 
  it 
  which 
  carries 
  the 
  

   larger 
  part 
  of 
  the 
  acid 
  radicals 
  of 
  the 
  soil 
  from 
  which 
  the 
  basic 
  radi- 
  

   cals 
  were 
  leached. 
  The 
  reunion 
  of 
  these 
  acids 
  with 
  the 
  alkalies 
  in 
  

   the 
  border 
  of 
  the 
  ocean 
  constitutes 
  a 
  critical 
  part 
  of 
  the 
  metamorphism 
  

   which 
  gives 
  rise 
  to 
  the 
  ocean 
  solutions 
  and 
  sediments. 
  We 
  will 
  

   return 
  to 
  this 
  presently. 
  

  

  3. 
  The 
  larger 
  part 
  of 
  the 
  solutions 
  now 
  flowing 
  into 
  the 
  ocean 
  

   comes 
  from 
  the 
  sediments; 
  the 
  lesser 
  part 
  from 
  the 
  igneous 
  rocks. 
  — 
  

   This 
  becomes 
  the 
  more 
  suggestive 
  when 
  it 
  is 
  noted 
  that 
  the 
  sediments 
  

   have 
  been 
  worked 
  over 
  repeatedly 
  in 
  some 
  notable 
  part; 
  some 
  small 
  

   part, 
  perhaps 
  hundreds 
  of 
  times; 
  some 
  larger 
  part, 
  scores 
  of 
  times; 
  

   while 
  some 
  other 
  large 
  part 
  perhaps 
  has 
  not 
  been 
  worked 
  more 
  than 
  

   once, 
  unless 
  we 
  count 
  in 
  the 
  many 
  times 
  most 
  material 
  is 
  handled 
  

   in 
  going 
  from 
  the 
  parent 
  rock 
  to 
  the 
  ocean. 
  That 
  the 
  sediments 
  

   should 
  still 
  be 
  able 
  to 
  yield 
  saline 
  solutions 
  to 
  the 
  observed 
  extent 
  

  

  10 
  C. 
  K. 
  Leith 
  and 
  W. 
  J. 
  Mead, 
  Metatnorphic 
  geology 
  (1915), 
  p. 
  69 
  et 
  seu.., 
  particularly 
  

   pp. 
  83-88. 
  

  

  