﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  121 
  

  

  or 
  more 
  in 
  diameter. 
  In 
  the 
  balls 
  they 
  show 
  but 
  little 
  sign 
  of 
  

   corrosive 
  action, 
  but 
  in 
  the 
  glassy, 
  intervening 
  matter 
  they 
  are 
  

   often 
  considerably 
  corroded 
  by 
  the 
  igneous 
  rock, 
  resulting 
  in 
  the 
  

   production 
  of 
  most 
  curious 
  shapes 
  (figure 
  n). 
  

  

  In 
  the 
  specimen 
  figured, 
  the 
  lava 
  attack 
  was 
  probably 
  from 
  the 
  

   front 
  instead 
  of 
  from 
  the 
  right 
  hand, 
  thus 
  lessening 
  the 
  amount 
  

   of 
  apparent 
  corrosion, 
  though 
  a 
  large 
  margin 
  remains. 
  These 
  cor- 
  

   roded 
  inclusions 
  are 
  in 
  the 
  pitchstone, 
  while 
  those 
  in 
  the 
  balls 
  

   show 
  but 
  little 
  corrosion 
  and 
  but 
  a 
  trifling 
  selvage 
  of 
  surrounding 
  

   glass. 
  

  

  The 
  two 
  matters 
  of 
  chief 
  interest 
  concerning 
  the 
  inclusions 
  are, 
  

   the 
  source 
  of 
  the 
  limestone 
  and 
  the 
  reason 
  for 
  the 
  absence 
  of 
  other 
  

   inclusions, 
  especially 
  those 
  of 
  shale. 
  

  

  The 
  limestone 
  of 
  these 
  inclusions 
  is 
  slightly 
  reddened, 
  presum- 
  

   ably 
  a 
  result 
  of 
  heat 
  from 
  the 
  lava, 
  and 
  is 
  finely 
  crystalline 
  in 
  

   texture, 
  likely 
  due 
  to 
  recrystallization 
  on 
  heating, 
  though 
  this 
  is 
  

   not 
  certain. 
  The 
  inclusions 
  are 
  all 
  of 
  the 
  one 
  type 
  of 
  limestone. 
  

   They 
  must 
  have 
  been 
  brought 
  up 
  from 
  below 
  ground 
  by 
  the 
  rising 
  

   lava, 
  which 
  must 
  have 
  passed 
  through 
  such 
  a 
  limestone 
  formation 
  

   during 
  its 
  ascent. 
  

  

  The 
  only 
  rock 
  formation 
  of 
  the 
  region 
  which 
  could 
  have 
  fur- 
  

   nished 
  such 
  material 
  is 
  the 
  Bald 
  Mountain 
  limestone 
  of 
  the 
  eastern 
  

   basin, 
  In 
  the 
  western 
  basin 
  deposits 
  we 
  have 
  the 
  Hoyt 
  and 
  Amster- 
  

   dam 
  limestones, 
  but 
  they 
  are 
  separated 
  by 
  the 
  great 
  thickness 
  of 
  

   the 
  Little 
  Falls 
  dolomite. 
  Had 
  the 
  inclusions 
  come 
  from 
  this 
  series 
  

   there 
  would 
  unquestionably 
  have 
  been 
  an 
  abundance 
  of 
  dolomite 
  

   fragments 
  in 
  the 
  lava, 
  while 
  actually 
  there 
  are 
  none. 
  But 
  the 
  

   Bald 
  Mountain 
  limestone 
  has 
  shales 
  above 
  and 
  below. 
  It 
  also 
  has 
  

   many 
  dolomite 
  beds 
  in 
  its 
  lower 
  portion, 
  so 
  that 
  it 
  is 
  surprising 
  

   that 
  there 
  are 
  none 
  in 
  the 
  lava, 
  if 
  the 
  inclusions 
  really 
  came 
  from 
  

   this 
  formation. 
  The 
  question 
  of 
  the 
  source 
  of 
  the 
  inclusions 
  

   becomes 
  of 
  much 
  importance 
  in 
  the 
  discussion 
  of 
  another 
  problem, 
  

   and 
  we 
  must 
  later 
  return 
  to 
  it. 
  

  

  The 
  knob 
  is 
  surrounded 
  by 
  black 
  shales, 
  chiefly 
  Normanskill, 
  

   and 
  it 
  would 
  seem 
  that 
  the 
  lava 
  must 
  have 
  risen 
  through 
  a 
  large 
  

   thickness 
  of 
  such 
  shale. 
  There 
  are 
  also 
  frequent 
  beds 
  of 
  hard, 
  

   sandy 
  grit 
  in 
  the 
  shale. 
  Under 
  the 
  circumstances 
  the 
  utter 
  lack 
  

   of 
  recognizable 
  shale 
  inclusions 
  is 
  most 
  astonishing. 
  There 
  are 
  

   some 
  large 
  masses 
  of 
  shale 
  involved 
  with 
  the 
  lava 
  but 
  it 
  is 
  ques- 
  

   tionable 
  if 
  they 
  can 
  be 
  regarded 
  as 
  inclusions. 
  There 
  are 
  a 
  few 
  

   grains 
  of 
  quartz 
  observable 
  in 
  the 
  thin 
  sections, 
  and 
  one 
  patch 
  

  

  