﻿482 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  reached. 
  The 
  relation 
  between 
  this 
  rock 
  and 
  the 
  syenite 
  has 
  

   been 
  carefully 
  sought 
  but 
  as 
  yet 
  not 
  conclusively 
  established 
  for 
  

   the 
  whole 
  area. 
  West 
  of 
  Natural 
  Bridge 
  in 
  Jefferson 
  co. 
  the 
  sye- 
  

   nite 
  unquestionably 
  passes 
  over 
  into 
  a 
  very 
  perfect 
  re$ 
  gneiss 
  

   as 
  described 
  in 
  the 
  paper 
  so 
  often 
  cited. 
  Both 
  in 
  the 
  field 
  and 
  

   under 
  the 
  microscope 
  the 
  gradual 
  change 
  of 
  the 
  rock 
  can 
  be 
  fol- 
  

   lowed 
  through 
  every 
  step. 
  But 
  in 
  the 
  region 
  now 
  under 
  discus- 
  

   sion 
  the 
  phenomena, 
  while 
  conclusive 
  in 
  regard 
  to 
  some 
  parts 
  of 
  

   the 
  gneiss, 
  are 
  not 
  so 
  for 
  others. 
  From 
  field 
  evidence 
  it 
  is 
  clear 
  

   that 
  the 
  hornblende 
  gneiss 
  adjacent 
  to 
  the 
  syenite 
  is 
  merely 
  a 
  

   modification 
  of 
  the 
  latter 
  rock, 
  the 
  passage 
  between 
  the 
  two 
  being 
  

   quite 
  gradual 
  with 
  no 
  break 
  of 
  any 
  kind. 
  Often 
  the 
  typical 
  red 
  

   gneiss 
  contains 
  large 
  feldspars 
  identical 
  with 
  those 
  of 
  the 
  syenite 
  

   and 
  evidently 
  a 
  residue 
  from 
  crushing. 
  These 
  portions 
  of 
  the 
  

   hornblende 
  gneiss 
  together 
  with 
  the 
  Natural 
  Bridge 
  occurrences 
  

   afford 
  instructive 
  examples 
  of 
  true 
  igneous 
  gneisses 
  younger 
  than 
  

   the 
  limestone 
  series. 
  

  

  But 
  farther 
  south 
  toward 
  the 
  Diana-Croghan 
  line 
  and 
  in 
  the 
  

   latter 
  town 
  there 
  are 
  large 
  areas 
  of 
  red 
  hornblende 
  gneiss, 
  

   coarser, 
  more 
  massive 
  and 
  more 
  quartzose 
  than 
  the 
  gneisses 
  

   clearly 
  derived 
  from 
  the 
  syenite. 
  They 
  more 
  closely 
  resemble 
  

   slightly 
  modified 
  hornblende 
  granites, 
  and 
  indeed 
  at 
  some 
  points, 
  

   as 
  for 
  instance 
  Jerden 
  Falls, 
  are 
  nothing 
  but 
  hornblende 
  granite 
  

   so 
  far 
  as 
  structure 
  and 
  composition 
  are 
  concerned. 
  While 
  there 
  

   is 
  no 
  doubt 
  that 
  the 
  syenite 
  passes 
  into 
  typical 
  gneisses 
  on 
  a 
  

   large 
  scale, 
  it 
  is 
  as 
  yet 
  uncertain 
  whether 
  these 
  extensive 
  areas 
  

   of 
  coarse 
  hornblende 
  gneiss 
  to 
  the 
  south 
  and 
  east 
  are 
  derived 
  

   from 
  it 
  or 
  belong 
  to 
  a 
  separate 
  period 
  of 
  intrusion. 
  In 
  either 
  

   event 
  there 
  is 
  doubtless 
  a 
  close 
  relationship 
  between 
  the 
  rocks. 
  

  

  These 
  coarse 
  and 
  rather 
  massive 
  gneisses 
  were 
  found 
  by 
  Mr 
  

   D. 
  H. 
  Newland, 
  working 
  under 
  the 
  writer's 
  direction, 
  to 
  continue 
  

   without 
  perceptible 
  break 
  into 
  southeastern 
  St 
  Lawrence 
  co. 
  

   beyond 
  Cranberry 
  lake 
  and 
  northward 
  into 
  the 
  towns 
  of 
  Russell, 
  

   Pierrepont 
  and 
  Parishville, 
  constituting 
  a 
  very 
  large 
  area. 
  Oc- 
  

   casionally 
  finer 
  banded 
  gneisses 
  probably 
  sedimentary 
  appear, 
  

   and 
  a 
  garnetiferous 
  amphibolite 
  similar 
  to 
  that 
  of 
  Warren 
  co. 
  

  

  