﻿Geology 
  and 
  Natural 
  History. 
  391 
  

  

  *'Such 
  an 
  element 
  is 
  sodium. 
  We 
  take 
  for 
  this 
  calculation 
  the 
  

   element 
  alone, 
  thus 
  avoiding 
  the 
  obscure 
  question 
  of 
  its 
  ionization, 
  

   which 
  does 
  not 
  concern 
  the 
  issue. 
  The 
  quantity 
  of 
  sodium 
  now 
  

   in 
  the 
  sea, 
  and 
  the 
  annual 
  rate 
  of 
  its 
  supply 
  by 
  the 
  rivers, 
  lead, 
  

   it 
  will 
  be 
  seen, 
  to 
  the 
  deduction 
  that 
  the 
  age 
  of 
  the 
  Earth 
  is 
  99 
  

   million 
  years. 
  Certain 
  deductions 
  from 
  this 
  are 
  — 
  it 
  will 
  be 
  shown 
  

   — 
  warranted, 
  so 
  that 
  the 
  final 
  result 
  of 
  this 
  paper 
  will 
  be 
  to 
  show 
  

   that 
  the 
  probable 
  age 
  is 
  about 
  89 
  million 
  years. 
  Also, 
  that 
  this 
  is 
  

   probably 
  a 
  major 
  limit, 
  and 
  that 
  considerable 
  departure 
  from 
  

   uniformity 
  of 
  activities 
  could 
  hardly 
  amend 
  it 
  to 
  less 
  than 
  80 
  

   million 
  years." 
  

  

  The 
  actual 
  calculation 
  is 
  very 
  simple, 
  since 
  in 
  the 
  first 
  place 
  the 
  

   total 
  mass 
  of 
  the 
  ocean 
  is 
  known 
  approximately 
  and 
  also 
  its 
  com- 
  

   position, 
  hence 
  the 
  total 
  amount 
  of 
  sodium 
  now 
  present 
  in 
  it 
  is 
  

   obtained 
  ; 
  further, 
  the 
  total 
  amount 
  of 
  water 
  discharged 
  by 
  the 
  

   rivers 
  into 
  the 
  ocean 
  is 
  known, 
  with 
  their 
  average 
  percentage 
  of 
  

   solid 
  matter, 
  sodium 
  included, 
  and 
  this 
  gives 
  the 
  mass 
  of 
  sodium 
  

   annually 
  added 
  to 
  the 
  ocean. 
  The 
  quotient 
  obtained 
  is 
  99,400,000 
  

   years. 
  

  

  A 
  minute 
  discussion 
  is 
  given 
  as 
  to 
  the 
  probable 
  original 
  condi- 
  

   tion 
  of 
  the 
  ocean 
  and 
  the 
  state 
  in 
  which 
  the 
  chlorine 
  now 
  com- 
  

   bined 
  as 
  sodium 
  chloride 
  probably 
  existed. 
  It 
  is 
  concluded 
  that 
  

   of 
  the 
  total 
  chlorine 
  in 
  the 
  original 
  ocean, 
  probably 
  some 
  14 
  per 
  

   cent 
  may 
  have 
  existed 
  as 
  sodium 
  chloride 
  derived 
  from 
  the 
  rapid 
  

   denudation 
  of 
  the 
  original 
  rocks. 
  This 
  conclusion 
  is 
  based 
  on 
  the 
  

   view 
  that 
  the 
  chlorine 
  now 
  in 
  the 
  ocean 
  must 
  have 
  been 
  originally 
  

   free 
  in 
  the 
  atmosphere 
  and 
  hydrosphere, 
  probably 
  combined 
  with 
  

   hydrogen. 
  The 
  first 
  result, 
  (1) 
  99-4 
  millions 
  of 
  years, 
  obtained, 
  

   as 
  stated, 
  on 
  the 
  assumption 
  that 
  no 
  free 
  acid, 
  existed 
  in 
  the 
  

   primeval 
  atmosphere 
  and 
  that 
  the 
  total 
  river 
  supply 
  of 
  sodium 
  

   was 
  derived 
  at 
  a 
  uniform 
  rate 
  from 
  the 
  rocks, 
  is 
  now 
  (2) 
  reduced 
  

   to 
  86-9 
  million, 
  assuming 
  that 
  the 
  free 
  acid 
  in 
  the 
  original 
  atmos- 
  

   phere 
  (see 
  above), 
  less 
  that 
  subsequently 
  supplied 
  by 
  rivers, 
  

   attacked 
  the 
  original 
  rocks 
  and 
  became 
  neutralized 
  in 
  a 
  negligible 
  

   time. 
  This 
  again 
  (3) 
  becomes 
  89 
  millions 
  if 
  a 
  period 
  of 
  acid 
  

   denudation 
  at 
  a 
  rate 
  five 
  times 
  the 
  average 
  rate 
  of 
  present 
  sub- 
  

   aerial 
  denudation 
  is 
  assumed. 
  And 
  finally 
  (4) 
  the 
  result 
  89'3 
  

   millions 
  of 
  years 
  is 
  obtained 
  in 
  a 
  fourth 
  assumption 
  that 
  10 
  p. 
  c. 
  

   of 
  the 
  sodium 
  chloride 
  in 
  the 
  river 
  discharge 
  was 
  derived 
  

   from 
  the 
  ocean. 
  

  

  Account 
  is 
  taken 
  of 
  the 
  deposits 
  of 
  rock 
  salt 
  at 
  various 
  points, 
  

   as, 
  for 
  instance, 
  the 
  salt 
  range 
  of 
  the 
  Punjab 
  ; 
  but 
  it 
  is 
  shown 
  

   that 
  the 
  amount 
  involved 
  is 
  relatively 
  so 
  small 
  as 
  not 
  to 
  seriously 
  

   affect 
  the 
  problem. 
  Other 
  points 
  are 
  also 
  considered, 
  as 
  to 
  the 
  

   probable 
  uniformity 
  of 
  denudation 
  by 
  solution 
  dependent 
  upon 
  

   land 
  area 
  and 
  rainfall 
  ; 
  also 
  the 
  solvent 
  denudation 
  of 
  the 
  ocean 
  

   itself; 
  but 
  for 
  the 
  details 
  of 
  these, 
  reference 
  must 
  be 
  made 
  to 
  the 
  

   original 
  memoir. 
  

  

  One 
  interesting 
  relation 
  brought 
  out 
  in 
  the 
  discussion 
  is 
  that 
  

   existing 
  between 
  the 
  soda 
  (Na^O) 
  and 
  potash 
  (K^O) 
  in 
  the 
  aver- 
  

  

  