﻿60 
  TWENTY-FIRST 
  REPORT 
  ON 
  THE 
  STATE 
  CABINET* 
  

  

  shapes 
  assumed 
  by 
  these 
  minerals 
  in 
  limestone, 
  and 
  especially 
  

   by 
  the 
  silicates 
  just 
  mentioned, 
  have 
  been 
  noticed 
  by 
  Naumann 
  

   and 
  Delesse, 
  among 
  others 
  ; 
  and 
  the 
  latter 
  observer 
  supposed 
  

   that 
  this 
  condition 
  might 
  be 
  due 
  to 
  a 
  repulsive 
  action 
  between 
  

   the 
  particles 
  of 
  the 
  silicates 
  and 
  the 
  surrounding 
  calcareous 
  mat- 
  

   ter 
  when 
  both 
  were 
  in 
  a 
  plastic 
  state 
  under 
  the 
  influence 
  of 
  water 
  

   and 
  heat. 
  The 
  observations 
  of 
  Dawson 
  and 
  myself, 
  and 
  the 
  

   latter 
  ones 
  of 
  Giimbel, 
  how 
  T 
  ever, 
  as 
  detailed 
  on 
  pages 
  43 
  and 
  44, 
  

   demonstrate 
  that 
  this 
  rounded 
  form, 
  in 
  many 
  cases, 
  at 
  least, 
  is 
  due 
  

   to 
  no 
  such 
  subsequent 
  action, 
  but 
  has 
  been 
  given 
  by 
  the 
  calcareous 
  

   organic 
  structure, 
  in 
  whose 
  chambers 
  these 
  silicates 
  were 
  origi- 
  

   nally 
  deposited. 
  It 
  would, 
  however, 
  be 
  premature 
  to 
  say 
  that 
  this 
  

   explanation 
  is 
  of 
  universal 
  application, 
  but 
  it 
  may 
  be 
  affirmed 
  in 
  

   general 
  terms, 
  that 
  certain 
  external 
  forces 
  have, 
  in 
  the 
  limestone 
  

   beds, 
  prevented 
  the 
  free 
  development 
  which 
  these 
  mineral 
  species 
  

   naturally 
  assume 
  while 
  in 
  the 
  veinstones. 
  On 
  the 
  contrary, 
  the 
  

   rounding 
  of 
  the 
  angles 
  of 
  certain 
  crystals, 
  to 
  the 
  exclusion 
  of 
  

   others, 
  is 
  due 
  to 
  a 
  partial 
  dissolution 
  of 
  the 
  previously 
  formed 
  

   crystals. 
  

  

  As 
  already 
  remarked, 
  it 
  is 
  impossible 
  to 
  draw 
  any 
  definite 
  line 
  

   between 
  the 
  veins 
  just 
  described 
  and 
  those 
  already 
  mentioned 
  as 
  

   placed 
  in 
  the 
  preceding 
  class, 
  and 
  generally 
  designated 
  as 
  granitic 
  

   veins. 
  Most 
  of 
  their 
  characteristic 
  minerals 
  are 
  common 
  to 
  the 
  

   two 
  classes, 
  and 
  it 
  is 
  easy 
  to 
  trace 
  a 
  gradual 
  change 
  from 
  the 
  

   typical 
  granitic 
  veins, 
  to 
  those 
  in 
  which 
  carbonate 
  of 
  lime 
  is 
  the 
  

   predominant 
  mineral, 
  and 
  which 
  are 
  to 
  the 
  crystalline 
  limestones 
  

   what 
  the 
  former 
  are 
  to 
  gneiss 
  and 
  mica-schist. 
  In 
  both 
  cases 
  I 
  

   conceive 
  that 
  they 
  derive 
  their 
  mineral 
  contents 
  from 
  the 
  adjacent 
  

   strata, 
  whose 
  fissures 
  they 
  fill, 
  and 
  are 
  entitled 
  to 
  the 
  name 
  of 
  

   segregated 
  veins. 
  In 
  both 
  cases, 
  also, 
  it 
  must 
  be 
  borne 
  in 
  mind 
  

   that 
  other 
  vacant 
  spaces 
  in 
  the 
  strata, 
  whether 
  resulting 
  from 
  con- 
  

   traction, 
  solution, 
  or 
  other 
  causes, 
  may 
  present 
  conditions 
  for 
  

   deposition 
  similar 
  to 
  those 
  of 
  fissures, 
  and 
  may 
  thus 
  give 
  rise 
  to 
  

   drusy 
  cavities, 
  or 
  to 
  detached 
  masses 
  of 
  crystalline 
  minerals 
  iden- 
  

   tical 
  to 
  those 
  of 
  the 
  veinstones. 
  This 
  view 
  of 
  the 
  origin 
  of 
  granitic 
  

   veins 
  from 
  solution, 
  and 
  their 
  distinction 
  from 
  intrusive 
  granites, 
  

   has 
  been 
  insisted 
  upon 
  by 
  me 
  in 
  the 
  Geology 
  of 
  Canada, 
  pages 
  

   477, 
  644, 
  and 
  since, 
  with 
  more 
  details, 
  in 
  my 
  Contributions 
  to 
  

   Litholog}' 
  in 
  the 
  American 
  Journal 
  of 
  Sceince 
  [2], 
  xxxvii, 
  252. 
  

  

  To 
  resume, 
  then, 
  it 
  may 
  be 
  said 
  that 
  besides 
  the 
  fissures 
  filled 
  

   with 
  igneous 
  injected 
  granite, 
  forming 
  what 
  may 
  be 
  distinguished 
  

  

  