﻿Report 
  of 
  tee 
  State 
  Geolog-ist. 
  6}$ 
  

  

  smaller 
  pond 
  forty 
  or 
  fifty 
  feet 
  lower 
  clown. 
  Their 
  outlets 
  join 
  

   at 
  a- 
  still 
  lower 
  point. 
  

  

  ^lany 
  of 
  these 
  valleys 
  mns: 
  have 
  been 
  outlined 
  in 
  pre-Cambrian 
  

   times, 
  for 
  we 
  find 
  in 
  instances 
  the 
  remains 
  of 
  Potsdam 
  sandstone 
  

   as 
  little 
  ireas, 
  far 
  back 
  from 
  the 
  Champlain 
  valley. 
  Such 
  appear 
  

   in 
  Crown 
  Poin: 
  and 
  Ticonderoga 
  and 
  are 
  brought 
  out 
  strongly 
  by 
  

   the 
  map. 
  They 
  usually 
  lie 
  along 
  some 
  p^esent 
  stream, 
  whose 
  

   valley 
  is 
  now 
  largely 
  filled 
  by 
  dr.ft. 
  TTe 
  have 
  even 
  found 
  in 
  one 
  

   or 
  two 
  cases 
  little 
  patches, 
  too 
  scnall 
  to 
  map, 
  in 
  isolation 
  from 
  

   any 
  other 
  exposure. 
  The 
  contour 
  maps, 
  when 
  ready, 
  will 
  enable 
  

   us 
  to 
  draw 
  seme 
  interesting 
  conclusions 
  about 
  the 
  present 
  altitudes 
  

   of 
  these 
  above 
  Lake 
  Champlain 
  and 
  about 
  the 
  earlier 
  spread 
  of 
  

   the 
  Potsdam, 
  where 
  it 
  has 
  now 
  been 
  washed 
  away. 
  

  

  Scheates 
  of 
  Classification. 
  

  

  In 
  describing 
  the 
  " 
  Primary 
  " 
  rocks 
  of 
  the 
  Adirondack 
  region, 
  

   Emmons, 
  in 
  184:2, 
  speaks 
  of 
  the 
  following 
  varieties, 
  of 
  which 
  those 
  

   in 
  italics 
  are 
  cited 
  as 
  occurring 
  in 
  Essex 
  countv. 
  

  

  I. 
  Unstratified 
  : 
  a, 
  Granite: 
  b, 
  Hyjpersthene 
  rock; 
  e, 
  Primitive 
  

   limestone; 
  d, 
  Serpentine; 
  e, 
  Eensselaerite. 
  

  

  II. 
  Stratified: 
  a, 
  Gneiss; 
  b. 
  Hornblende 
  (i. 
  e. 
  hornblendic 
  gneiss); 
  

   c, 
  Sienite; 
  d, 
  Talc 
  or 
  steatite. 
  

  

  III. 
  Subordinate: 
  a, 
  Porphyry; 
  b, 
  Trap; 
  c, 
  Magnetic 
  oxide 
  of 
  

   iron; 
  d, 
  Specular 
  oxide 
  or 
  iron. 
  

  

  Emmons 
  says 
  little 
  of 
  the 
  respective 
  ages 
  of 
  the 
  subdivisions, 
  

   and 
  while 
  we 
  must 
  pay 
  a 
  well-deserved 
  tribute 
  to 
  the 
  great 
  

   industry 
  and 
  ability 
  that 
  he 
  displayed, 
  he 
  yet 
  had 
  some 
  concep- 
  

   tions 
  of 
  these 
  rocks 
  which 
  we 
  do 
  not 
  hold 
  to-day. 
  Thus 
  we 
  

   would 
  not 
  consider 
  the 
  limestones 
  as 
  igneous 
  rock, 
  nor 
  class 
  with 
  

   the 
  "Primary,'' 
  porphyries 
  that 
  penetrate 
  the 
  Utica 
  slate. 
  

  

  Dr. 
  T. 
  S. 
  Hunt 
  described, 
  in 
  IS 
  71, 
  the 
  Mineralogy 
  of 
  the 
  Lauren- 
  

   tian 
  limestones 
  (Twenty-first 
  Ann. 
  Eep. 
  X.Y. 
  State 
  Mus. 
  Xat. 
  Hist., 
  

   p. 
  47), 
  but 
  said 
  little 
  of 
  stratigraphical 
  moment. 
  Prof. 
  James 
  

   Hall 
  read 
  before 
  the 
  American 
  Association 
  at 
  Buffalo 
  in 
  1S76, 
  

   a 
  paper 
  on 
  the 
  Age 
  of 
  the 
  Serpentinous 
  Limestones 
  of 
  Xorthern 
  

   Xew 
  York, 
  of 
  which 
  but 
  a 
  brief 
  abstract 
  was 
  printed. 
  Prof. 
  Hall 
  

   speaks 
  of 
  tnem 
  as 
  later 
  than 
  the 
  Laurentian 
  and 
  earlier 
  than 
  the 
  

   Potsdam. 
  In 
  1S79, 
  C. 
  E. 
  Hall 
  wrote 
  upon 
  the 
  Laurentian 
  Mag- 
  

   netic 
  Iron 
  Ore 
  Deposits 
  in 
  Northern 
  Xew 
  York. 
  (Thirty-second 
  

  

  