﻿and 
  its 
  Significance 
  as 
  to 
  their 
  Origin. 
  45 
  

  

  the 
  chief 
  function 
  is 
  ascribed, 
  while 
  in 
  certain 
  cases 
  it 
  is 
  con- 
  

   sidered 
  probable 
  that 
  magmatic 
  carbon-dioxide 
  may 
  have 
  been 
  

   effective, 
  in 
  the 
  absence 
  of 
  limestone. 
  

  

  It 
  need 
  hardly 
  be 
  said 
  that 
  the 
  present 
  hypothesis 
  is 
  not 
  offered 
  

   in 
  controversion 
  of 
  any 
  of 
  those 
  above 
  mentioned, 
  but 
  merely 
  

   as 
  a 
  suggestion 
  arising 
  from 
  viewing 
  the 
  problem 
  from 
  another 
  

   standpoint. 
  As 
  a 
  matter 
  of 
  fact, 
  the 
  several 
  hypotheses 
  have 
  

   certain 
  features 
  in 
  common, 
  despite 
  great 
  differences 
  of 
  

   emphasis, 
  and 
  it 
  is 
  entirely 
  possible 
  that 
  all 
  the 
  various 
  agencies 
  

   appealed 
  to 
  may 
  play 
  a 
  part 
  in 
  the 
  complex 
  operations 
  under 
  

   consideration. 
  

  

  While 
  not 
  explicitly 
  stated, 
  the 
  writer 
  has, 
  throughout 
  the 
  

   discussion, 
  implied 
  the 
  belief 
  that 
  the 
  mineralizers 
  are 
  mag- 
  

   matic 
  or 
  "juvenile*' 
  rather 
  than 
  resurgent. 
  It 
  would, 
  indeed, 
  

   be 
  difficult 
  to 
  reconcile 
  any 
  other 
  view 
  with 
  the 
  hypothesis 
  as 
  

   here 
  presented. 
  This 
  is 
  clearly 
  indicated 
  by 
  the 
  previous 
  

   statement 
  to 
  the 
  effect 
  that 
  the 
  magmas 
  are 
  regarded 
  as 
  con- 
  

   taining 
  within 
  themselves 
  the 
  agents 
  of 
  differentiation. 
  Indeed, 
  

   the 
  hypothesis 
  is 
  merely 
  a 
  particular 
  application 
  of 
  the 
  broad 
  

   principle 
  that 
  magmatic 
  gases 
  are 
  a 
  large 
  and 
  vital 
  factor 
  in 
  

   the 
  system 
  of 
  terrestrial 
  circulation. 
  

  

  In 
  this 
  respect, 
  the 
  hypothesis 
  is 
  fundamentally 
  different 
  from 
  

   that 
  of 
  Daly, 
  since 
  it 
  implies 
  potential 
  alkaline 
  magmas 
  any- 
  

   where, 
  without 
  reference 
  to 
  the 
  nature 
  of 
  associated 
  sediments 
  

   or 
  even 
  to 
  the 
  existence 
  of 
  any 
  sediments 
  whatever 
  ; 
  while 
  

   Daly 
  regards 
  the 
  formation 
  of 
  alkaline 
  rocks 
  as 
  dependent, 
  in 
  

   most 
  cases, 
  upon 
  the 
  presence 
  of 
  limestones 
  which 
  furnish 
  the 
  

   necessary 
  carbon-dioxide. 
  

  

  Thus 
  far, 
  che 
  question 
  as 
  to 
  which 
  mineralizers 
  were 
  most 
  

   potent 
  as 
  agents 
  of 
  differentiation 
  has 
  not 
  been 
  considered, 
  

   this 
  being, 
  not 
  only 
  a 
  most 
  obscure 
  matter, 
  but 
  also 
  of 
  second- 
  

   ary 
  importance. 
  Viewing 
  the 
  mineralizers 
  as 
  magmatic, 
  it 
  is 
  

   probable, 
  on 
  general 
  grounds, 
  that 
  water, 
  above 
  the 
  critical 
  

   temperature, 
  or 
  even, 
  at 
  some 
  stages, 
  dissociated, 
  was 
  a 
  large, 
  

   if 
  not 
  the 
  largest, 
  factor. 
  According 
  to 
  Arrhenius,* 
  aqueous 
  

   gas 
  would 
  tend 
  to 
  extract 
  carbonic 
  acid, 
  hydrogen 
  sulphide, 
  

   combinations 
  of 
  univalent 
  ions, 
  such 
  as 
  those 
  of 
  chlorine, 
  

   fluorine 
  and 
  boron, 
  with 
  the 
  most 
  positive 
  ions, 
  like 
  the 
  alkali 
  

   metals, 
  rare 
  earths 
  and, 
  less 
  often, 
  the 
  alkaline 
  earth 
  metals. 
  

   In 
  other 
  words, 
  water, 
  under 
  magmatic 
  conditions, 
  tends 
  to 
  

   extract 
  the 
  elements 
  characteristic 
  of 
  the 
  alkaline 
  rocks, 
  rather 
  

   than 
  those 
  of 
  thesubalkaline 
  rocks 
  and, 
  at 
  the 
  same 
  time, 
  tends 
  

   to 
  concentrate 
  the 
  mineralizers. 
  

  

  Of 
  special 
  agents 
  suggested 
  by 
  the 
  composition 
  of 
  the 
  alkaline 
  

   rocks, 
  and 
  of 
  some 
  of 
  their 
  accessory 
  minerals, 
  chlorine 
  is 
  

   indicated 
  as 
  having 
  played 
  a 
  leading 
  part, 
  with 
  sulphur, 
  as 
  S0 
  3 
  , 
  

  

  * 
  S. 
  Arrhenius 
  : 
  Zur 
  PliYsik 
  der 
  Tulkanismus, 
  Geol. 
  Foren. 
  Forh., 
  xxii, 
  

   p. 
  247, 
  1900. 
  

  

  