﻿Geology 
  and 
  Mineralogy. 
  71 
  

  

  ciated 
  sandstone, 
  have 
  afforded 
  Dr. 
  C. 
  E. 
  Beecher 
  Lower 
  Cam- 
  

   brian 
  fossils 
  ; 
  and 
  that 
  in 
  one 
  case 
  the 
  sandstone 
  contained, 
  near 
  

   by, 
  the 
  mineral 
  graphite. 
  The 
  main 
  purpose 
  of 
  the 
  article 
  is 
  to 
  

   give 
  the 
  evidence 
  obtained 
  by 
  the 
  "author 
  in 
  favor 
  of 
  the 
  conclu- 
  

   sion 
  that 
  the 
  white 
  crystalline 
  limestone 
  of 
  the 
  county, 
  containing 
  

   chondrodite 
  and 
  other 
  minerals, 
  which 
  has 
  been 
  supposed 
  to 
  be 
  

   Archaean, 
  is 
  really 
  of 
  the 
  age 
  of 
  the 
  blue 
  limestone. 
  The 
  evidence 
  

   given 
  is, 
  briefly, 
  the 
  occurrence 
  of 
  graphite 
  in 
  both 
  the 
  white 
  and 
  

   blue 
  limestones 
  ; 
  the 
  passage 
  of 
  one 
  into 
  the 
  other 
  at 
  some 
  

   localities 
  ; 
  and 
  the 
  inference 
  that 
  the 
  white 
  limestone 
  owes 
  its 
  

   crystallization 
  to 
  contact 
  with 
  eruptive 
  rocks, 
  (granite, 
  etc.), 
  and 
  

   exhibits 
  various 
  contact 
  phenomena. 
  The 
  Franklinite 
  iron 
  ore- 
  

   bed 
  of 
  the 
  county 
  is 
  associated 
  with 
  the 
  white 
  limestone, 
  and 
  is 
  

   made 
  therefore 
  of 
  the 
  same 
  age. 
  The 
  conclusion 
  is 
  a 
  wide- 
  

   reaching 
  one, 
  and 
  the 
  facts 
  should 
  have 
  full 
  investigation 
  before 
  

   it 
  is 
  adopted. 
  The 
  evidence 
  drawn 
  from 
  the 
  graphite 
  is 
  of 
  un- 
  

   certain 
  value 
  as 
  the 
  mineral 
  occurs 
  in 
  rocks 
  of 
  much 
  later 
  time. 
  

   Prof. 
  Cook 
  regarded 
  the 
  iron 
  ore 
  beds 
  and 
  the 
  limestones 
  as 
  part 
  

   of 
  the 
  gneissic 
  formation 
  of 
  the 
  region, 
  the 
  gneiss 
  being 
  not 
  in 
  

   his 
  view 
  foliated 
  granite 
  ; 
  and 
  the 
  writer's 
  examinations 
  of 
  the 
  

   rocks 
  associated 
  with 
  these 
  ores 
  have 
  led 
  him 
  to 
  the 
  same 
  con- 
  

   clusion. 
  Moreover, 
  it 
  is 
  an 
  impossibility 
  that 
  the 
  crystallization 
  

   of 
  the 
  white 
  limestone 
  formation 
  should 
  have 
  been 
  produced 
  by 
  

   contact 
  with 
  the 
  dikes 
  of 
  igneous 
  rocks, 
  or 
  even 
  with 
  protruded 
  

   granite 
  ; 
  for 
  the 
  rock 
  of 
  a 
  dike 
  cools 
  outside 
  too 
  rapidly 
  for 
  such 
  

   a 
  result. 
  The 
  trap 
  dikes 
  of 
  New 
  Jersey 
  illustrate 
  this 
  point 
  

   abundantly. 
  Melted 
  granite 
  injected 
  through 
  a 
  cold 
  rock 
  would 
  

   not 
  be 
  true 
  crystalline 
  granite 
  against 
  the 
  walls 
  or 
  make 
  the 
  

   limestone 
  adjoining 
  coarsely 
  crystalline, 
  like 
  the 
  white 
  limestone, 
  

   even 
  for 
  a 
  hundred 
  feet. 
  Again 
  dikes 
  of 
  a 
  hornblendic 
  scapolite 
  

   rock 
  are 
  described. 
  But 
  it 
  is 
  impossible 
  that 
  melted 
  scapolite 
  

   injected 
  into 
  cold 
  rocks 
  in 
  fissures 
  four 
  to 
  six 
  feet 
  wide 
  or 
  wider 
  

   than 
  this, 
  should 
  become 
  on 
  cooling 
  crystallized 
  scapolite, 
  even 
  

   of 
  a 
  granular 
  form, 
  alike 
  from 
  wall 
  to 
  wall, 
  with 
  " 
  perfect 
  folia- 
  

   tion" 
  parallel 
  to 
  the 
  walls, 
  so 
  that 
  it 
  has 
  been 
  mistaken 
  for 
  

   gneiss. 
  For 
  such 
  crystallization 
  the 
  enclosing 
  limestone 
  should 
  

   be 
  hot 
  enough 
  for 
  its 
  own 
  crystallization 
  — 
  the 
  condition 
  attend- 
  

   ing 
  metamorphism. 
  

  

  The 
  actual 
  passage 
  of 
  the 
  blue 
  limestone 
  into 
  the 
  white 
  has 
  

   weight, 
  if 
  the 
  observation 
  is 
  beyond 
  question. 
  The 
  writer 
  

   doubts 
  the 
  conclusion 
  as 
  to 
  actual 
  passage 
  because 
  he 
  has 
  ob- 
  

   served 
  in 
  East 
  Lee, 
  Massachusetts, 
  an 
  apparent 
  passage 
  of 
  the 
  

   kind 
  between 
  the 
  Stockbridge 
  limestone 
  and 
  another 
  which 
  is 
  

   chondroditic, 
  and 
  saved 
  himself 
  from 
  inferring 
  their 
  identity 
  by 
  

   finding 
  the 
  latter 
  associated 
  in 
  a 
  part 
  of 
  the 
  area 
  with 
  a 
  very 
  

   different 
  class 
  of 
  crystalline 
  schists. 
  In 
  other 
  cases 
  over 
  eastern 
  

   Berkshire 
  chondroditic 
  limestone 
  was 
  met 
  with 
  ; 
  and 
  in 
  each 
  it 
  

   was 
  associated 
  with 
  rocks 
  that 
  were 
  in 
  part 
  so 
  unlike 
  the 
  schists 
  

   of 
  the 
  Stockbridge 
  limestone 
  or 
  Taconic 
  belt, 
  viewing 
  them 
  

   through 
  its 
  whole 
  course, 
  from 
  Vermont, 
  Massachusetts, 
  and 
  

  

  