﻿Il6 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  This 
  occurrence 
  of 
  volcanic 
  rock 
  merits 
  detailed 
  description, 
  both 
  

   because 
  it 
  is 
  unique 
  and 
  because 
  it 
  is 
  puzzling. 
  It 
  is 
  unlike 
  any 
  

   other 
  known 
  occurrence 
  of 
  igneous 
  rock 
  in 
  the 
  State 
  or 
  in 
  the 
  

   neighboring 
  states. 
  

  

  Woodworth's 
  original 
  description 
  of 
  the 
  knob 
  is 
  so 
  excellent 
  

   that 
  we 
  can 
  not 
  do 
  better 
  than 
  to 
  quote 
  freely 
  from 
  it: 
  

  

  The 
  right 
  bank 
  of 
  the 
  Hudson 
  river 
  here 
  consists 
  of 
  the 
  usual 
  bluff 
  of 
  

   Hudson 
  River 
  slates 
  partly 
  masked 
  by 
  Pleistocene 
  clays. 
  The 
  igneous 
  rock, 
  

   being 
  more 
  resistant 
  to 
  erosion 
  than 
  the 
  fragile 
  slates, 
  has 
  withstood 
  better 
  

   the 
  glacial 
  erosion 
  to 
  which 
  the 
  region 
  has 
  been 
  subjected 
  and 
  therefore 
  stands 
  

   out 
  as 
  a 
  sort 
  of 
  buttress 
  from 
  the 
  main 
  wall 
  of 
  the 
  inner 
  Hudson 
  valley 
  or 
  

   gorge. 
  Much 
  like 
  the 
  volcanic 
  necks 
  and 
  plugs 
  about 
  Edinburgh 
  in 
  Scotland, 
  

   this 
  hard 
  mass 
  has 
  been 
  deeply 
  scoured 
  at 
  base 
  on 
  the 
  ice-struck 
  side. 
  In 
  

   fact, 
  all 
  of 
  the 
  present 
  relief 
  of 
  this 
  plug 
  and 
  the 
  adjacent 
  river 
  valley 
  is 
  due 
  

   to 
  the 
  action 
  of 
  the 
  river 
  combined 
  with 
  that 
  of 
  the 
  ice 
  sheet 
  of 
  the 
  glacial 
  

   period. 
  

  

  The 
  summit 
  of 
  the 
  knob 
  scarcely 
  attains 
  the 
  level 
  of 
  the 
  upland 
  which 
  lies 
  

   west 
  of 
  the 
  river. 
  A 
  slight 
  depression 
  west 
  of 
  the 
  plug 
  serves 
  to 
  give 
  it 
  the 
  

   appearance 
  of 
  a 
  low 
  knob 
  when 
  viewed 
  from 
  the 
  upland, 
  but 
  at 
  a 
  distance 
  

   it 
  is 
  relatively 
  inconspicuous. 
  This 
  fact, 
  taken 
  in 
  connection 
  with 
  the 
  dark 
  

   color 
  of 
  the 
  rock 
  in 
  which, 
  respect 
  it 
  closely 
  resembles 
  the 
  adjacent 
  Hudson 
  

   series, 
  perhaps 
  accounts 
  for 
  its 
  going 
  so 
  long 
  unnoticed 
  or 
  at 
  least 
  un- 
  

   described 
  by 
  the 
  geologists 
  who 
  have 
  passed 
  through 
  the 
  upper 
  Hudson 
  

   valley. 
  There 
  is 
  no 
  mention 
  of 
  the 
  knob 
  by 
  Peter 
  Kalm 
  or 
  later 
  observers; 
  

   yet 
  it 
  appears 
  from 
  Brandon's 
  historical 
  map 
  of 
  Old 
  Saratoga 
  that 
  General 
  

   Stark 
  of 
  the 
  American 
  army 
  occupied 
  the 
  eastern 
  base 
  of 
  this 
  knob 
  during 
  

   the 
  Battle 
  of 
  Saratoga. 
  

  

  Stark's 
  knob 
  igneous 
  mass 
  lies 
  surrounded 
  on 
  the 
  ground 
  by 
  the 
  Hudson 
  

   River 
  (Normanskill) 
  slates. 
  These 
  are 
  highly 
  inclined, 
  cleaved, 
  and 
  much 
  

   broken 
  rocks 
  with 
  a 
  general 
  northeast 
  strike. 
  So 
  far 
  as 
  my 
  own 
  observations 
  

   go, 
  there 
  are 
  no 
  small 
  dikes 
  radiating 
  from 
  the 
  main 
  igneous 
  mass 
  into 
  

   the 
  adjacent 
  cleaved 
  sedimentary 
  rocks, 
  nor 
  are 
  there 
  any 
  noticeable 
  signs 
  

   of 
  metamorphism 
  in 
  these 
  rocks 
  attributable 
  to 
  the 
  heating 
  action 
  of 
  the 
  

   lavas 
  in 
  the 
  plug. 
  The 
  Hudson 
  river 
  group 
  throughout 
  this 
  region 
  is 
  some- 
  

   what 
  altered, 
  but 
  not 
  more 
  so 
  at 
  ^Stark's 
  knob 
  than 
  remote 
  from 
  it. 
  . 
  . 
  . 
  

   This 
  lack 
  of 
  contact 
  metamorphism, 
  unless 
  such 
  alteration 
  be 
  limited 
  to 
  

   baking, 
  which 
  was 
  not 
  observed 
  in 
  the 
  accessible 
  portion 
  of 
  the 
  contact, 
  and 
  

   the 
  failure 
  of 
  apophyses 
  or 
  branching 
  dikes, 
  are 
  points 
  of 
  little 
  value 
  in 
  

   determining 
  the 
  origin 
  of 
  the 
  igneous 
  rock 
  in 
  the 
  knob. 
  It 
  remains 
  to 
  

   determine 
  by 
  other 
  evidences 
  whether 
  the 
  rock 
  is 
  intrusive 
  or 
  extrusive. 
  

  

  On 
  the 
  southeast 
  side 
  of 
  the 
  igneous 
  mass 
  and 
  dissecting 
  its 
  border 
  are 
  two 
  

   faults 
  ; 
  that 
  on 
  the 
  eastern 
  side 
  strikes 
  n. 
  9 
  e., 
  that 
  on 
  the 
  southeast, 
  n. 
  54 
  e. 
  

   The 
  southeastern 
  fault 
  is 
  downthrown 
  on 
  the 
  northwest, 
  as 
  on 
  this 
  side 
  there 
  

   is 
  to 
  be 
  seen 
  the 
  slate 
  underlying 
  a 
  mass 
  of 
  trap 
  on 
  the 
  southeast 
  of 
  the 
  

   fault. 
  The 
  complete 
  relations 
  of 
  the 
  igneous 
  to 
  the 
  sedimentary 
  rocks 
  on 
  

   this 
  side 
  are 
  not 
  shown. 
  Figure 
  9, 
  which 
  is 
  a 
  diagrammatic 
  representation 
  

   of 
  the 
  cross 
  section 
  of 
  the 
  knob 
  and 
  its 
  peculiar 
  internal 
  structure, 
  shows 
  

  

  