﻿704 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  cisely 
  the 
  case, 
  for 
  thus 
  far 
  very 
  few 
  outcrops 
  of 
  sandstone 
  have 
  

   been 
  seen 
  within 
  the 
  gneissic 
  areas. 
  This 
  fact 
  is 
  well 
  shown 
  on 
  

   the 
  map. 
  

  

  It 
  may 
  be 
  well 
  to 
  sum 
  up 
  briefly 
  the 
  foregoing 
  conclusions. 
  If 
  

   the 
  iron 
  ores 
  be 
  regarded 
  as 
  formed 
  by 
  the 
  replacement 
  of 
  lime- 
  

   stone 
  by 
  iron 
  deiived 
  from 
  decomposing 
  pyrite, 
  a 
  sufficient 
  

   explanation 
  is 
  afforded 
  for 
  the 
  form, 
  character 
  and 
  distribution 
  

   of 
  the 
  deposits, 
  for 
  the 
  association 
  of 
  granite 
  with 
  many 
  of 
  them, 
  

   for 
  an 
  unusual 
  alteration 
  of 
  this 
  granite, 
  and 
  for 
  the 
  presence 
  of 
  

   Potsdam 
  sandstone 
  resting 
  upon 
  the 
  ore. 
  Of 
  the 
  other 
  theories 
  

   suggested, 
  while 
  each 
  explains 
  some 
  of 
  these 
  facts, 
  neither 
  one 
  

   satisfactorily 
  explains 
  all 
  of 
  them. 
  The 
  weak 
  point 
  in 
  the 
  theory 
  

   advanced 
  lies 
  in 
  the 
  unavoidable 
  scantiness 
  of 
  data 
  upon 
  which 
  

   it 
  is 
  based, 
  and 
  the 
  writer 
  fully 
  realizes 
  that 
  it 
  may 
  be 
  proved 
  

   untenable 
  by 
  more 
  extended 
  investigation. 
  It 
  has 
  been 
  presented 
  

   at 
  some 
  length, 
  because 
  it 
  seems 
  to 
  afford 
  the 
  most 
  rational 
  

   explanation 
  of 
  the 
  facts 
  thus 
  far 
  ob 
  served, 
  bringing 
  them 
  into 
  

   clear 
  and 
  definite 
  relation 
  with 
  each 
  other. 
  This 
  certainly 
  gives 
  

   it 
  a 
  right 
  to 
  be 
  accepted 
  as 
  a 
  working 
  hypothesis, 
  to 
  be 
  retained 
  

   until 
  disproved. 
  

  

  That 
  the 
  hypothesis 
  is 
  not 
  in 
  the 
  least 
  a 
  novel 
  one 
  need 
  

   hardly 
  be 
  said, 
  for 
  the 
  same 
  explanation 
  has 
  been 
  applied 
  to 
  a 
  

   great 
  many 
  ore 
  deposits 
  in 
  various 
  parts 
  of 
  the 
  world. 
  It 
  would 
  

   be 
  useless 
  to 
  try 
  to 
  cite 
  all 
  of 
  these 
  cases, 
  but 
  a 
  few 
  may 
  be 
  

   briefly 
  mentioned. 
  Many 
  of 
  the 
  limonites 
  of 
  the 
  Great 
  Valley 
  

   have 
  been 
  ascribed 
  to 
  the 
  replacement 
  of 
  limestone 
  by 
  iron 
  

   derived 
  from 
  oxidizing 
  pyrite, 
  and 
  Prime* 
  in 
  describing 
  the 
  

   deposits 
  of 
  Lehigh 
  county, 
  Pennsylvania, 
  outlines 
  the 
  process 
  in 
  

   almost 
  the 
  same 
  words 
  used 
  above 
  by 
  the 
  writer. 
  The 
  main 
  

   difference 
  in 
  the 
  two 
  localities 
  is 
  that 
  the 
  Pennsylvania 
  deposits 
  

   have 
  damourite 
  slate 
  instead 
  of 
  granite 
  as 
  the 
  underlying 
  

   impervious 
  rock. 
  Emmons 
  f 
  in 
  his 
  classic 
  monograph 
  on 
  the 
  

   Leadville 
  region 
  describes 
  limonite 
  and 
  hematite 
  of 
  similar 
  

   origin, 
  the 
  iron 
  coming 
  from 
  pyrite 
  and 
  replacing 
  limestone. 
  

   The 
  hematites 
  of 
  the 
  Marquette 
  district, 
  Lake 
  Superior, 
  as 
  

   shown 
  by 
  Yan 
  Hise4 
  have 
  been 
  formed 
  by 
  a 
  different 
  process 
  of 
  

  

  *F. 
  Prime, 
  Jr., 
  On 
  the 
  occurrence 
  of 
  brown 
  hematite 
  deposits 
  of 
  the 
  Great 
  Valley, 
  Amer. 
  

   Jour. 
  Sci. 
  (3) 
  IX, 
  p. 
  433. 
  

  

  + 
  S. 
  F. 
  Emmons. 
  U. 
  S. 
  G. 
  S. 
  Monograph, 
  XII, 
  pp. 
  499, 
  547. 
  

  

  % 
  C. 
  R. 
  Van 
  Hise, 
  The 
  Iron 
  Ores 
  of 
  the 
  Marquette 
  District, 
  Michigan, 
  Amer. 
  Jour. 
  Sci. 
  (8) 
  

   XLKI, 
  p. 
  116. 
  

  

  