﻿GEOLOGY 
  OF 
  SARATOGA 
  SPRINGS 
  AND 
  VICINITY 
  Iig 
  

  

  been 
  removed 
  since 
  our 
  previous 
  visit; 
  between 
  this 
  and 
  1912 
  yet 
  

   more 
  was 
  removed, 
  until 
  now 
  comparatively 
  little 
  of 
  the 
  volcanic 
  

   rock 
  remains 
  above 
  ground. 
  In 
  addition 
  to 
  our 
  own 
  study 
  of 
  the 
  

   occurrence 
  we 
  have 
  had 
  the 
  advantage 
  of 
  visiting 
  it 
  with 
  other 
  

   geologists, 
  with 
  Van 
  Ingen 
  and 
  with 
  Smyth 
  in 
  1910, 
  with 
  Kemp 
  

   in 
  191 
  1 
  and 
  with 
  Woodworth 
  in 
  1912. 
  

  

  The 
  result 
  of 
  opening 
  up 
  the 
  knob 
  has 
  been 
  to 
  bring 
  to 
  light 
  

   certain 
  structural 
  features 
  that 
  Woodworth 
  could 
  not 
  possibly 
  

   have 
  observed 
  in 
  1901, 
  and 
  to 
  furnish 
  fresher 
  material 
  for 
  micro- 
  

   scopic 
  and 
  chemical 
  study 
  than 
  was 
  available 
  to 
  him. 
  Other 
  

   features 
  showed 
  better 
  on 
  the 
  old, 
  weathered 
  surface 
  of 
  the 
  rock 
  

   than 
  in 
  the 
  fresher 
  interior. 
  

  

  Constitution 
  of 
  the 
  knob. 
  The 
  knob 
  consists 
  of 
  lava 
  balls, 
  large 
  

   and 
  small, 
  with 
  intervening 
  material. 
  The 
  balls 
  range 
  up 
  to 
  2 
  feet 
  

   in 
  diameter. 
  At 
  the 
  time 
  of 
  our 
  first 
  visit 
  many 
  of 
  them 
  lay 
  about, 
  

   being 
  broken 
  up 
  by 
  the 
  quarrymen. 
  In 
  these 
  we 
  were 
  unable, 
  to 
  

   verify 
  Woodworth's 
  observation 
  that 
  they 
  consisted 
  of 
  a 
  dense 
  

   exterior 
  and 
  more 
  porous 
  nucleus, 
  though 
  these 
  two 
  layers 
  ap- 
  

   peared 
  plainly 
  on 
  the 
  weathered 
  surfaces 
  which 
  he 
  saw. 
  A 
  prob- 
  

   able 
  reason 
  for 
  this 
  may 
  be 
  that 
  in 
  quarrying, 
  this 
  exterior 
  crust 
  

   comes 
  away 
  with 
  the 
  intervening 
  matter, 
  leaving 
  the 
  balls 
  free 
  

   from 
  it. 
  The 
  deforming 
  agencies 
  which 
  have 
  acted 
  upon 
  the 
  

   knob 
  may 
  well 
  have 
  had 
  this 
  result. 
  The 
  balls, 
  as 
  we 
  saw 
  them, 
  

   always 
  had 
  slickensided 
  exteriors, 
  and 
  consisted 
  throughout 
  of 
  

   similar 
  material. 
  Judging 
  from 
  all 
  the 
  data, 
  it 
  seems 
  probable 
  

   to 
  us 
  that 
  the 
  balls 
  had 
  originally 
  a 
  glassy 
  crust 
  and 
  finely 
  crystal- 
  

   line 
  interior, 
  and 
  that 
  shearing 
  has 
  separated 
  the 
  crust 
  and 
  nucleus 
  

   so 
  that 
  they 
  do 
  not 
  come 
  away 
  together 
  in 
  quarrying. 
  For 
  the 
  

   most 
  part 
  the 
  balls 
  consist 
  of 
  dense, 
  black 
  rock, 
  so 
  finely 
  crystal- 
  

   line 
  that 
  crystals 
  are 
  neither 
  visible 
  to 
  the 
  eye 
  nor 
  to 
  the 
  lens. 
  

   Exteriorly 
  the 
  balls 
  v 
  are 
  occasionally 
  amygdaloidal, 
  but 
  there 
  is 
  

   no 
  great 
  quantity 
  having 
  such 
  texture. 
  

  

  The 
  intervening 
  material 
  has 
  been 
  badly 
  sheared 
  and 
  crushed, 
  

   so 
  that 
  much 
  of 
  it 
  has 
  the 
  appearance 
  of 
  slickensided, 
  shaly 
  matter. 
  

   But 
  some 
  of 
  it 
  is 
  less 
  damaged, 
  especially 
  in 
  the 
  vicinity 
  of 
  lime- 
  

   stone 
  inclusions, 
  which 
  seem 
  to 
  have 
  acted 
  to 
  prevent 
  crushing; 
  

   and 
  here 
  the 
  rock 
  is 
  always 
  of 
  glassy 
  texture, 
  a 
  black 
  pitchstone. 
  

   This 
  is 
  also 
  sometimes 
  amygdaloidal 
  ; 
  and 
  this 
  amygdaloidal 
  glass 
  

   differs 
  so 
  greatly 
  in 
  appearance 
  from 
  the 
  other 
  amygdaloid, 
  that 
  

   we 
  took 
  it 
  in 
  the 
  field 
  for 
  variolite. 
  This, 
  however, 
  it 
  does 
  not 
  

   seem 
  to 
  be. 
  

  

  