﻿648 
  Forty-seventh 
  Report 
  on 
  the 
  State 
  Museum. 
  

  

  southern 
  central 
  portion, 
  331, 
  is 
  a 
  large 
  mass 
  not 
  entirely 
  

   fresh, 
  and 
  showing 
  hornblende, 
  pyroxene, 
  plagioclase 
  and 
  a 
  

   little 
  biotite. 
  In 
  the 
  northwestern 
  area 
  a 
  most 
  interesting 
  

   intrusion 
  is 
  met, 
  that 
  differs 
  from 
  any 
  thing 
  elsewhere 
  noted. 
  A 
  

   mass 
  of 
  very 
  coarsely 
  porphyritic 
  rock, 
  with 
  feldspar 
  phenocrysts 
  

   two 
  to 
  three 
  inches 
  in 
  diameter 
  in 
  a 
  ground 
  mass 
  of 
  hornblende 
  and 
  

   plagioclase, 
  has 
  penetrated 
  the 
  limestone 
  series. 
  The 
  phenocrysts 
  

   are 
  aggregates 
  of 
  smaller 
  individuals, 
  now 
  much 
  altered. 
  The 
  

   entire 
  intrusion 
  is 
  at 
  least 
  twenty 
  feet 
  thick, 
  but 
  there 
  are 
  other 
  

   parallel 
  dikes 
  a 
  few 
  feet 
  distant, 
  which 
  are 
  less. 
  No. 
  346, 
  three 
  

   miles 
  away, 
  is 
  a 
  narrow 
  one, 
  which, 
  while 
  showing 
  a 
  dioritic 
  

   mineralogical 
  composition 
  and 
  structure, 
  is 
  yet 
  of 
  the 
  same 
  

   general 
  type 
  as 
  the 
  gabbros. 
  

  

  Series 
  IV. 
  All 
  the 
  divisions 
  of 
  the 
  palaeozoic 
  as 
  before 
  referred 
  to 
  

   are 
  represented. 
  The 
  most 
  interesting 
  of 
  all 
  is 
  the 
  Potsdam 
  sand- 
  

   stone, 
  because 
  of 
  the 
  little 
  remnants 
  which 
  now 
  remain 
  at 
  the 
  

   heads 
  of 
  the 
  two 
  inland 
  valleys. 
  The 
  one 
  away 
  up 
  in 
  the 
  central 
  

   part 
  of 
  the 
  town 
  is 
  the 
  most 
  isolated 
  outcrop 
  we 
  have 
  seen, 
  and 
  as 
  

   stated 
  earlier, 
  is 
  probably 
  the 
  surviving 
  remnant 
  of 
  a 
  tongue 
  

   which 
  extended 
  southward 
  from 
  Penfield 
  pond. 
  "When 
  the 
  

   contour 
  maps 
  are 
  available, 
  it 
  will 
  be 
  interesting 
  to 
  determine 
  

   the 
  relative 
  altitudes 
  and 
  the 
  maximum 
  movements 
  which 
  the 
  

   Potsdam 
  has 
  suffered. 
  The 
  exposures 
  along 
  Trout 
  brook 
  are 
  of 
  

   the 
  same 
  character, 
  and 
  they 
  indicate 
  that 
  the 
  valley 
  is 
  a 
  pre- 
  

   Cambrian 
  depression. 
  The 
  Potsdam 
  again 
  appears 
  southwest 
  of 
  

   Mt. 
  Defiance. 
  It 
  is 
  succeeded 
  to 
  the 
  north 
  by 
  the 
  Calciferous 
  

   which 
  is 
  much 
  faulted. 
  The 
  Calciferous 
  extends 
  well 
  back 
  of 
  

   Ticonderoga 
  village, 
  but 
  in 
  the 
  village, 
  along 
  the 
  river, 
  the 
  

   Potsdam 
  shows 
  beneath 
  it. 
  The 
  Utica 
  slate 
  forms 
  two 
  miles 
  of 
  

   shore 
  above 
  the 
  old 
  fort.* 
  North 
  of 
  this 
  the 
  Chazy 
  is 
  again 
  

   developed 
  both 
  near 
  the 
  shore 
  and 
  inland. 
  A 
  small 
  patch 
  of 
  

   Calci 
  erous 
  likewise 
  shows 
  at 
  230. 
  

  

  Series 
  V. 
  ISTo 
  representative 
  of 
  this 
  series 
  was 
  found. 
  

  

  Series 
  VI. 
  The 
  glacial 
  and 
  pust 
  glacial 
  deposits 
  are 
  quite 
  

   extensive, 
  especially 
  along 
  Lake 
  Champlain. 
  The 
  latter 
  are 
  clays, 
  

   and 
  mask 
  the 
  geology 
  to 
  a 
  great 
  extent. 
  C. 
  E. 
  Hall 
  speaks 
  of 
  a 
  

   great 
  moraine 
  near 
  Putnam's 
  pond, 
  and 
  explains 
  Lake 
  George 
  as 
  

  

  * 
  For 
  detailed 
  g«olo£y 
  of 
  the 
  area 
  for 
  a 
  mile 
  or 
  two 
  around 
  the 
  old 
  fort 
  and 
  to 
  the 
  south, 
  see 
  

   Brained 
  and 
  Se^ly, 
  Bull. 
  Amer. 
  Mus. 
  Nat. 
  Hist., 
  June, 
  1890, 
  III, 
  p. 
  10. 
  

  

  