﻿658 
  FORTY-SEVEJNTH 
  REPORT 
  ON 
  THE 
  STATE 
  MUSEUM. 
  

  

  Potsdam. 
  Just 
  what 
  the 
  relations 
  of 
  the 
  serpentine 
  are, 
  does 
  

   not 
  appear, 
  the 
  facts 
  having 
  been 
  noted 
  by 
  my 
  assistant, 
  Mr. 
  

   Tenner. 
  

  

  Series 
  III. 
  The 
  anorthosites 
  constitute 
  nearly 
  the 
  entire 
  town- 
  

   ship. 
  They 
  form 
  a 
  great 
  ridge 
  along 
  the 
  lake, 
  known 
  as 
  Trem- 
  

   bleau 
  mountain, 
  which 
  is 
  somewhat 
  broken 
  at 
  Port 
  Douglass 
  by 
  

   a 
  cross 
  valley. 
  In 
  the 
  interior 
  is 
  Bos 
  worth 
  mountain, 
  and 
  back 
  

   of 
  this 
  the 
  rugged 
  Poke-a-Moonshine 
  ridge. 
  The 
  rocks 
  are 
  green 
  

   anortht 
  site 
  in 
  general, 
  often 
  gneissoid. 
  The 
  cuts 
  of 
  the 
  Delaware 
  

   and 
  Hudson 
  railroad, 
  afford 
  fine 
  exposures 
  along 
  the 
  lake, 
  and 
  the 
  

   developments 
  in 
  quarries 
  for 
  " 
  Ausable 
  granite," 
  as 
  it 
  is 
  called, 
  near 
  

   Keeseville 
  give 
  a 
  number 
  of 
  openings. 
  This 
  rich 
  green 
  feldspathic 
  

   variety 
  cpntains 
  plagioclase, 
  and 
  green 
  pyroxene 
  with 
  a 
  few 
  shreds 
  

   of 
  hypersthene, 
  and 
  an 
  occasional 
  garnet. 
  It 
  has 
  proved 
  a 
  hand- 
  

   some 
  building 
  stone, 
  and 
  has 
  found 
  wide 
  use, 
  although 
  at 
  

   present 
  the 
  quarries 
  are 
  shut 
  down. 
  Along 
  the 
  lake 
  the 
  anor- 
  

   thosites 
  occasionally 
  show 
  crushed 
  strips 
  or 
  shear-zones 
  which 
  

   have 
  developed 
  a 
  granular 
  mass 
  of 
  pyroxene, 
  plagioclase 
  and 
  

   garnet, 
  with 
  a 
  somewhat 
  schistose 
  structure. 
  Eiotite 
  appears 
  in 
  

   the 
  southeastern 
  exposures. 
  The 
  gneissoid 
  portions 
  are 
  the 
  usual 
  

   banded 
  aggregates 
  of 
  hornblende, 
  plagioclase 
  and 
  subordinate 
  

   pyroxene. 
  In 
  the 
  quarries 
  near 
  Keeseville, 
  quartz 
  can 
  be 
  

   detected. 
  So 
  far 
  as 
  the 
  lake 
  shore 
  is 
  concerned, 
  the 
  rocks 
  of 
  

   Series 
  III 
  do 
  not 
  appear 
  again 
  north 
  of 
  Port 
  Kent, 
  but 
  give 
  way 
  

   to 
  the 
  palaeozoic 
  sediments. 
  

  

  Series 
  IV 
  The 
  Potsdam 
  sandstone 
  is 
  the 
  only 
  member 
  of 
  this 
  

   series 
  present. 
  It 
  sets 
  back 
  along 
  the 
  Ausable 
  river 
  to 
  a 
  point 
  

   above 
  Keeseville. 
  In 
  the 
  Ausable 
  chasm 
  it 
  affords 
  one 
  of 
  the 
  

   finest 
  sections 
  of 
  this 
  formation 
  of 
  the 
  State. 
  Fossils 
  occur, 
  but 
  

   are 
  not 
  abundant. 
  The 
  small 
  remnant 
  of 
  supposed 
  Potsdam 
  at 
  

   55, 
  west 
  of 
  Port 
  Douglass 
  was 
  referred 
  to 
  under 
  Series 
  II. 
  

  

  Series 
  V. 
  An 
  immense 
  number 
  of 
  diabase 
  dikes 
  penetrate 
  the 
  

   anorthosites 
  along 
  the 
  lake 
  shore, 
  and 
  every 
  railway 
  cut 
  shows 
  

   them. 
  One 
  was 
  also 
  met 
  in 
  the 
  quarries 
  at 
  the 
  north 
  end 
  of 
  

   Augur 
  pond 
  (No. 
  13); 
  another 
  at 
  16 
  southeast 
  of 
  Keeseville, 
  

   and 
  a 
  third 
  in 
  the 
  limestone 
  at 
  Trout 
  Pond. 
  

  

  Series 
  VI. 
  The 
  sands 
  and 
  gravels 
  are 
  best 
  developed 
  along 
  

   the 
  northern 
  boundary. 
  A 
  fine 
  bank 
  with 
  marine 
  shells 
  (Saxicava, 
  

   etc.) 
  is 
  exposed 
  along 
  the 
  railway 
  south 
  of 
  Port 
  Kent. 
  Much 
  

  

  