﻿694 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  the 
  scarcity 
  of 
  data 
  available 
  at 
  the 
  mines. 
  The 
  outcrops 
  are 
  

   generally 
  very 
  un&atisfactory, 
  and 
  the 
  rocks 
  highly 
  altered, 
  and 
  

   often 
  of 
  doubtful 
  character. 
  At 
  the 
  time 
  of 
  the 
  writer's 
  visit 
  

   the 
  difficulties 
  were 
  increased 
  by 
  the 
  fact 
  that 
  all 
  the 
  mines 
  were 
  

   shut 
  down 
  and 
  most 
  of 
  them 
  flooded. 
  Moreover, 
  it 
  was 
  found 
  

   impossible 
  to 
  procure 
  any 
  drawings 
  or 
  details 
  of 
  the 
  workings. 
  

  

  At 
  only 
  one 
  mine, 
  the 
  Old 
  Sterling, 
  were 
  at 
  all 
  satisfactory 
  

   data 
  collected, 
  and 
  even 
  here 
  much 
  was 
  to 
  be 
  desired. 
  It 
  follows 
  

   that 
  the 
  conclusions 
  reached 
  are 
  largely 
  based 
  upon 
  the 
  facts 
  as 
  

   shown 
  at 
  this 
  locality 
  and 
  much 
  is 
  inferred 
  as 
  regards 
  other 
  

   mines. 
  Bat, 
  while 
  there 
  are 
  many 
  local 
  variations, 
  there 
  is 
  such 
  

   a 
  strong 
  general 
  resemblance 
  in 
  the 
  deposits 
  of 
  the 
  various 
  

   mines 
  that 
  it 
  seems 
  almost 
  certain 
  that 
  they 
  must 
  have 
  had 
  a 
  

   common 
  origin. 
  

  

  Upon 
  examination 
  and 
  comparison 
  of 
  the 
  important 
  mines 
  of 
  

   the 
  region 
  it 
  becomes 
  apparent 
  that 
  any 
  satisfactory 
  explanation 
  

   of 
  the 
  origin 
  of 
  the 
  deposits 
  must 
  account 
  for 
  several 
  facts 
  in 
  

   regard 
  to 
  the 
  mode 
  of 
  occurrence 
  of 
  the 
  ores 
  and 
  associated 
  

   rocks, 
  which 
  seem 
  to 
  be 
  intimately 
  connected 
  and 
  constant 
  

   features. 
  Of 
  these 
  facts 
  the 
  more 
  important 
  are 
  the 
  presence 
  of 
  

   the 
  Potsdam 
  sandstone, 
  resting 
  upon 
  and 
  grading 
  into 
  the 
  ore, 
  

   the 
  linear 
  distribution 
  of 
  the 
  deposits 
  along 
  the 
  strike, 
  the 
  

   irregularity 
  in 
  the 
  form 
  of 
  the 
  ore 
  bodies 
  and 
  variation 
  in 
  the 
  

   character 
  of 
  the 
  ore, 
  the 
  common 
  presence 
  of 
  granite 
  intrusions 
  

   in 
  the 
  ore, 
  a 
  remarkable 
  alteration 
  of 
  this 
  granite, 
  together 
  with 
  

   other 
  indications 
  of 
  much 
  chemical 
  action. 
  

  

  The 
  presence 
  of 
  the 
  sandstone 
  forming 
  the 
  cap 
  and 
  grading 
  

   down 
  into 
  the 
  ore 
  was 
  one 
  of 
  the 
  first 
  facts 
  noted 
  in 
  studying 
  

   the 
  deposits. 
  So 
  constant 
  did 
  this 
  seem 
  to 
  be 
  that 
  it 
  was 
  thought 
  

   there 
  miTst 
  be 
  some 
  genetic 
  connection 
  between 
  the 
  rocks. 
  As 
  

   it 
  was 
  evident 
  that 
  the 
  ore 
  lay 
  in, 
  not 
  on, 
  the 
  crystalline 
  rocks, 
  

   it 
  could 
  not 
  be 
  regarded 
  as 
  contemporaneous 
  with 
  the 
  sandstone. 
  

   The 
  first 
  explanation 
  of 
  association 
  that 
  offered 
  itself 
  was 
  that 
  

   an 
  originally 
  ferruginous 
  sandstone 
  was 
  deposited 
  upon 
  lime- 
  

   stone, 
  that 
  underground 
  waters 
  containing 
  carbon 
  dioxide, 
  

   organic 
  acids, 
  etc., 
  passing 
  through 
  the 
  sandstone 
  dissolved 
  the 
  

   iron 
  and 
  carried 
  it 
  down 
  to 
  the 
  limestone, 
  where 
  the 
  iron 
  

   replaced 
  the 
  lime 
  and 
  by 
  subsequent 
  changes 
  became 
  hematite. 
  

   While 
  this 
  hypothesis 
  explains 
  the 
  association 
  of 
  ore 
  and 
  sand- 
  

  

  