﻿Report 
  of 
  the 
  State 
  Geologist. 
  693 
  

  

  were 
  sent 
  to 
  various 
  iron 
  centers 
  for 
  mixture 
  with 
  more 
  refrac- 
  

   tory 
  ores. 
  At 
  the 
  present 
  time 
  the 
  depression 
  in 
  the 
  iron 
  business 
  

   and 
  great 
  development 
  of 
  richer 
  ores 
  combine 
  to 
  render 
  the 
  

   working 
  of 
  these 
  mines 
  unprofitable. 
  

  

  The 
  question 
  of 
  the 
  origin 
  of 
  these 
  ores 
  has 
  never 
  been 
  settled, 
  

   nor, 
  in 
  fact, 
  discussed 
  at 
  any 
  length 
  since 
  the 
  early 
  days 
  of 
  the 
  

   New 
  York 
  Geological 
  Survey. 
  At 
  that 
  time 
  Emmons* 
  gave 
  

   with 
  some 
  detail 
  his 
  reasons 
  for 
  regarding 
  the 
  ores, 
  together 
  

   with 
  the 
  associated 
  so-called 
  serpentine, 
  as 
  irruptive. 
  Yanuxem,f 
  

   who 
  studied 
  more 
  particularly 
  the 
  ores 
  in 
  Lewis 
  county, 
  consid- 
  

   ered 
  them 
  rather 
  superficial 
  concentrations, 
  lying 
  between 
  the 
  

   crystalline 
  rocks 
  and 
  the 
  Potsdam 
  sandstone 
  and 
  as 
  closely 
  con- 
  

   nected 
  with 
  the 
  latter 
  as 
  with 
  the 
  former. 
  At 
  a 
  much 
  later 
  date 
  

   Brooks;}; 
  examined 
  the 
  Eossie 
  mines 
  and 
  concluded 
  that 
  they 
  

   showed 
  a 
  continuous 
  series 
  of 
  sedimentary 
  deposits, 
  including 
  

   sandstone, 
  ore, 
  magnesian 
  rock 
  {serpentine 
  of 
  Emmons), 
  and 
  

   crystalline 
  limestone, 
  together 
  with 
  some 
  granite. 
  Still 
  later 
  

   Smock 
  § 
  states 
  that 
  there 
  are 
  probably 
  two 
  classes 
  of 
  ore 
  deposits, 
  

   the 
  original 
  sediments 
  and 
  secondary 
  concentrations, 
  but 
  he 
  does 
  

   not 
  give 
  the 
  facts 
  upon 
  which 
  his 
  inferences 
  are 
  based. 
  Kimball 
  || 
  

   states 
  that 
  the 
  ores 
  are 
  the 
  result 
  of 
  replacement 
  of 
  limestone 
  

   but 
  gives 
  no 
  description 
  of 
  their 
  mode 
  of 
  occurrence 
  other 
  than 
  

   to 
  say 
  that 
  he 
  examined 
  particularly 
  a 
  mass 
  of 
  specular 
  ore 
  in 
  

   Pierpont, 
  which 
  was 
  in 
  crystalline 
  limestone 
  of 
  Calciferous 
  age. 
  

   This 
  determination 
  of 
  the 
  age 
  of 
  the 
  crystalline 
  limestone 
  is 
  

   doubtless 
  incorrect. 
  

  

  It 
  is 
  thus 
  evident 
  that 
  there 
  has 
  been 
  much 
  diversity 
  of 
  opinion 
  

   in 
  regard 
  to 
  the 
  origin 
  of 
  the 
  ores, 
  among 
  those 
  who 
  have 
  studied 
  

   them. 
  While 
  the 
  writer 
  scarcely 
  feels 
  prepared 
  to 
  draw 
  final 
  

   conclusions 
  from 
  the 
  work 
  thus 
  far 
  done 
  by 
  him 
  on 
  these 
  deposits, 
  

   it 
  may 
  be 
  worth 
  while 
  to 
  state 
  some 
  of 
  the 
  facts 
  observed, 
  

   together 
  with 
  what 
  seems 
  at 
  least 
  a 
  reasonable 
  explanation 
  of 
  

   them. 
  

  

  That 
  the 
  problem 
  is 
  not 
  simple 
  is 
  evident 
  from 
  the 
  variety 
  of 
  

   opinions 
  expressed 
  in 
  regard 
  to 
  it. 
  The 
  great 
  difficulty 
  lies 
  in 
  

  

  * 
  E. 
  Emmons, 
  Geology 
  of 
  New 
  York, 
  2d 
  District, 
  p. 
  97. 
  

   t 
  L. 
  Vanuxem, 
  Geology 
  of 
  New 
  York, 
  3d 
  District, 
  p. 
  267. 
  

   JT. 
  B. 
  Brooks, 
  Am. 
  Jour. 
  Sci. 
  (3), 
  IV, 
  p. 
  22. 
  

   § 
  J. 
  C. 
  Smock, 
  Bull. 
  N. 
  Y. 
  State 
  Museum, 
  No. 
  7, 
  p. 
  10. 
  , 
  

  

  1 
  J. 
  P. 
  Kimball, 
  Genesis 
  of 
  iron 
  ores 
  by 
  isomorphous 
  and 
  pseudomorphous 
  replacement 
  of 
  

   limestone, 
  etc., 
  Amer. 
  Geol., 
  VIII, 
  p. 
  368. 
  

  

  