﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  131 
  

  

  known. 
  It 
  is 
  quite 
  possible 
  therefore 
  that 
  it 
  is 
  here 
  one 
  of 
  the 
  

   primary 
  minerals 
  of 
  the 
  lava. 
  But 
  the 
  comparatively 
  large 
  amount 
  

   present, 
  together 
  with 
  the 
  rarity 
  of 
  its 
  occurrence 
  in 
  igneous 
  rocks, 
  

   enforces 
  caution 
  in 
  attributing 
  such 
  a 
  source 
  to 
  it. 
  In 
  so 
  far 
  as 
  

   possible 
  derivation 
  from 
  the 
  snale 
  is 
  concerned 
  it 
  must 
  be 
  stated 
  

   that 
  the 
  associated 
  shales 
  in 
  the 
  vicinity 
  of 
  the 
  knob 
  show 
  no 
  indi- 
  

   cation 
  of 
  any 
  loss 
  of 
  carbon 
  due 
  to 
  action 
  of 
  the 
  lava, 
  or 
  indeed 
  

   of 
  any 
  change 
  whatever, 
  so 
  that 
  if 
  we 
  look 
  to 
  them 
  as 
  a 
  source 
  

   we 
  must 
  assume 
  that 
  the 
  process 
  only 
  took 
  place 
  at 
  greater 
  depths. 
  

   It 
  would 
  be 
  a 
  debatable 
  question 
  whether 
  hydrocarbons, 
  liberated 
  

   from 
  the 
  shales 
  by 
  the 
  heat 
  of 
  the 
  intrusion, 
  would 
  migrate 
  into 
  

   the 
  lava; 
  whether 
  they 
  would 
  not 
  rather 
  be 
  driven 
  away 
  from 
  it. 
  

   Even 
  if 
  taken 
  up 
  why 
  should 
  they 
  have 
  been 
  converted 
  to 
  graphite 
  ? 
  

   ■All, 
  or 
  nearly 
  all 
  lavas 
  contain 
  carbon; 
  but 
  on 
  cooling 
  they 
  give 
  it 
  

   off 
  in 
  combination 
  with 
  oxygen, 
  or 
  with 
  hydrogen. 
  Why 
  an 
  excep- 
  

   tion 
  was 
  made 
  in 
  this 
  case 
  we 
  cannot 
  say. 
  

  

  Is 
  the 
  lava 
  in 
  place? 
  Stark's 
  knob 
  is 
  a 
  small 
  mass 
  of 
  igneous 
  

   rock 
  inclosed 
  in 
  shales. 
  The 
  shales 
  are 
  greatly 
  contorted 
  and 
  com- 
  

   pressed 
  everywhere, 
  and 
  the 
  evidence, 
  both 
  structural 
  and 
  paleon- 
  

   tologic, 
  shows 
  that 
  they 
  have 
  been 
  overthrust 
  into 
  the 
  district 
  

   from 
  the 
  east. 
  The 
  question 
  naturally 
  arises, 
  May 
  not 
  the 
  igneous 
  

   rock 
  have 
  come 
  into 
  the 
  region 
  by 
  overthrusting, 
  along 
  with 
  the 
  

   inclosing 
  shales? 
  We 
  regret 
  that 
  we 
  are 
  unable 
  definitely 
  to 
  an- 
  

   swer 
  this 
  question. 
  Were 
  it 
  true, 
  certain 
  of 
  the 
  structural 
  features 
  

   would 
  receive 
  a 
  simple 
  explanation. 
  The 
  shearing 
  and 
  disloca- 
  

   tion 
  of 
  the 
  rock 
  would 
  thus 
  be 
  accounted 
  for, 
  as 
  well 
  as 
  its 
  abrupi 
  

   termination 
  laterally, 
  and 
  the 
  lack 
  of 
  dikes 
  running 
  out 
  from 
  it 
  

   into 
  the 
  shales. 
  We 
  could 
  understand 
  the 
  reason 
  for 
  the 
  shale 
  

   wedges 
  inclosed 
  in 
  the 
  lava. 
  More 
  latitude 
  would 
  be 
  given 
  in 
  

   accounting 
  for 
  the 
  inclusions, 
  abundance 
  of 
  limestone 
  of 
  a 
  single 
  

   type 
  and 
  absence 
  of 
  all 
  other 
  rocks. 
  The 
  manner 
  of 
  occurrence 
  

   in 
  the 
  shales, 
  a 
  short 
  and 
  comparatively 
  thick 
  mass 
  of 
  lava 
  im- 
  

   prisoned 
  in 
  shales 
  along 
  their 
  dip, 
  would 
  also 
  not 
  be 
  so 
  hard 
  to 
  

   understand. 
  The 
  shales 
  are 
  so 
  cleaved 
  that 
  they 
  usually 
  come 
  

   apart 
  more 
  readily 
  on 
  the 
  cleavage 
  planes 
  than 
  on 
  the 
  stratifica- 
  

   tion. 
  It 
  is 
  this 
  character 
  that 
  makes 
  it 
  so 
  difficult 
  to 
  collect 
  fossils 
  

   from 
  them. 
  It 
  would 
  seem 
  that 
  the 
  explosive 
  action 
  of 
  a 
  vol- 
  

   canic 
  vent 
  breaking 
  through 
  them 
  would 
  have 
  opened 
  them 
  verti- 
  

   cally 
  along 
  the 
  cleavage 
  planes 
  instead 
  of 
  following 
  the 
  incline 
  of 
  

   the 
  dip. 
  

  

  