﻿670 
  lORTY- 
  SEVENTH 
  REPORT 
  ON 
  THE 
  STATE 
  MUSEUM. 
  

  

  2d, 
  a 
  series 
  of 
  crystalline 
  limestones 
  and 
  associated 
  gneisses, 
  

   also 
  of 
  pre-Cambrian 
  age 
  ; 
  

  

  3d, 
  a 
  mass 
  of 
  coarsely 
  crystalline 
  gabbro 
  or 
  norite, 
  (the 
  anortho- 
  

   site 
  of 
  Adams), 
  also 
  pre 
  Cambrian 
  ; 
  

  

  4th, 
  the 
  Potsdam 
  sandstone, 
  of 
  great 
  but 
  unknown 
  thickness, 
  

   of 
  upper 
  Cambrian 
  age, 
  overlying 
  unconformably 
  any 
  one 
  of 
  

   the 
  first 
  three 
  groups; 
  

  

  5th, 
  the 
  sandy 
  dolomites 
  of 
  the 
  Calciferous 
  sandstone, 
  whose 
  

   thickness 
  in 
  Clinton 
  county 
  is 
  unknown, 
  but 
  which, 
  further 
  south, 
  

   have 
  a 
  thickness 
  of 
  1500 
  feet 
  ; 
  

  

  6th, 
  the 
  Trenton 
  limestone 
  formation, 
  locally 
  divisible 
  into 
  the 
  

   Chazy, 
  Black 
  River 
  and 
  Trenton 
  limestones, 
  readily 
  distinguishable 
  

   by 
  their 
  contained 
  fossils 
  ; 
  the 
  Birdseye 
  limestone, 
  which 
  elsewhere 
  

   may 
  be 
  separated 
  from 
  the 
  Chazy 
  and 
  Black 
  River, 
  not 
  present- 
  

   ing 
  its 
  distinctive 
  characters 
  in 
  this 
  district 
  ; 
  

  

  7th, 
  the 
  Hudson 
  River 
  group, 
  represented 
  at 
  but 
  a 
  single 
  

   locality 
  by 
  calcareous 
  black 
  slates 
  which 
  carry 
  the 
  fauna 
  of 
  the 
  

   lower 
  portion 
  of 
  this 
  group, 
  the 
  Utica 
  slate. 
  In 
  the 
  area 
  so 
  far 
  

   studied 
  and 
  mapped, 
  all 
  these 
  formations 
  are 
  present 
  but 
  the 
  

   pre-Cambrian 
  limestone, 
  series 
  No. 
  2. 
  

  

  The 
  pre-Cambrian 
  rocks 
  which, 
  in 
  Essex 
  county 
  to 
  the 
  south 
  

   reach 
  the 
  shore 
  of 
  Lake 
  Champlain, 
  recede 
  rapidly 
  from 
  the 
  

   lake 
  in 
  Clinton 
  county, 
  and 
  are 
  confined 
  to 
  its 
  southwest 
  

   portion. 
  Cambrian 
  and 
  Silurian 
  rocks 
  underlie 
  all 
  the 
  county 
  

   east 
  and 
  north 
  in 
  a 
  broad 
  belt 
  which 
  swings 
  round 
  the 
  north- 
  

   eastern 
  foothills 
  of 
  the 
  Adirondacks. 
  The 
  altitude 
  of 
  this 
  belt 
  

   is 
  low 
  on 
  the 
  east, 
  thence 
  with 
  a 
  quite 
  rapid 
  rise 
  as 
  the 
  pre- 
  

   Cambrian 
  area 
  is 
  approached. 
  On 
  the 
  north 
  the 
  belt 
  is 
  higher 
  

   and 
  the 
  rise 
  more 
  regular 
  and 
  even. 
  In 
  the 
  tier 
  of 
  townships 
  

   bordering 
  on 
  Lake 
  Champlain, 
  therefore, 
  the 
  altitude 
  is 
  slight, 
  

   and 
  only 
  on 
  their 
  extreme 
  western 
  border 
  are 
  the 
  edges 
  of 
  the 
  

   first 
  pre-Cambrian 
  outliers 
  met 
  with. 
  Embayments 
  of 
  Potsdam 
  

   sandstone 
  lie 
  in 
  the 
  valleys 
  between 
  these 
  outliers, 
  precisely 
  

   simiLir 
  in 
  occurrence 
  to 
  those 
  bordering 
  on 
  the 
  lake 
  in 
  Essex 
  

   county. 
  The 
  townships 
  comprised 
  on 
  the 
  maps 
  are 
  Champlain, 
  

   Chazy, 
  Beekmantown, 
  Plattsburgh 
  and 
  Schuyler 
  Falls, 
  with 
  

   portions 
  of 
  Mooers, 
  Altona 
  and 
  Peru. 
  In 
  Champlain, 
  Chazy, 
  

   Mooers 
  and 
  Altona 
  outcrops 
  are 
  of 
  sufficient 
  frequency 
  to 
  permit 
  

   the 
  delineation 
  of 
  the 
  surface 
  boundaries 
  between 
  the 
  various 
  

  

  