﻿De 
  Witt, 
  near 
  Syracuse, 
  New 
  York. 
  457 
  

  

  excavation 
  of 
  the 
  reservoir. 
  They 
  present 
  signs 
  of 
  slight 
  meta- 
  

   morphism, 
  consisting 
  of 
  increase 
  in 
  hardness 
  and 
  darkening 
  in 
  

   color. 
  Mr. 
  Schneider 
  has 
  called 
  my 
  attention 
  to 
  an 
  exposure 
  

   600 
  yards 
  north 
  of 
  the 
  reservoir, 
  in 
  which 
  there 
  is 
  considerable 
  

   flexing 
  in 
  the 
  shales, 
  but 
  this 
  was 
  the 
  only 
  signs 
  of 
  disturbance 
  

   noted 
  and 
  may 
  not 
  be 
  due 
  to 
  the 
  intrusion. 
  

  

  The 
  intrusive 
  rock 
  contains 
  many 
  inclusions 
  of 
  various 
  rocks 
  

   which 
  will 
  be 
  referred 
  to 
  by 
  Prof. 
  Kemp. 
  They 
  were 
  of 
  

   course 
  brought 
  up 
  from 
  below 
  by 
  the 
  dike. 
  

  

  The 
  relations 
  of 
  the 
  Dewitt 
  dike 
  to 
  the 
  Syracuse 
  occurrence 
  

   are 
  not 
  known, 
  but 
  as 
  the 
  rocks 
  and 
  relations 
  are 
  so 
  similar 
  it 
  

   is 
  probable 
  that 
  they 
  are 
  connected 
  underground. 
  It 
  is 
  very 
  

   desirable 
  that 
  a 
  careful 
  search 
  should 
  be 
  made 
  in 
  the 
  region 
  for 
  

   other 
  dikes 
  at 
  the 
  surface. 
  

  

  Petrography 
  of 
  the 
  Dewitt 
  Dike. 
  

   J. 
  F. 
  Kemp. 
  

  

  The 
  interest 
  of 
  geologists 
  was 
  greatly 
  excited 
  when 
  Dr. 
  Gr. 
  

   H. 
  Williams 
  announced, 
  in 
  1887, 
  the 
  undoubted 
  igneous 
  nature 
  

   of 
  the 
  serpentine, 
  which, 
  in 
  1839 
  had 
  been 
  recorded 
  by 
  Van- 
  

   uxem 
  as 
  occurring 
  in 
  the 
  Salina 
  salt 
  group 
  at 
  Syracuse, 
  E". 
  Y. 
  

   The 
  region 
  of 
  undisturbed 
  sedimentary 
  strata 
  of 
  central 
  New 
  

   York 
  was 
  generally 
  regarded, 
  with 
  much 
  reason, 
  as 
  one 
  of 
  the 
  

   least 
  likely 
  of 
  all 
  localities 
  to 
  contain 
  intrusive 
  rocks 
  ; 
  and 
  

   although 
  scattered 
  mention 
  of 
  dikes 
  had 
  been 
  made 
  for 
  at 
  least 
  

   two 
  other 
  localities, 
  the 
  microscopic 
  determinations 
  of 
  Dr. 
  

   Williams 
  were 
  the 
  first 
  really 
  conclusive 
  evidence 
  of 
  their 
  

   igneous 
  character. 
  In 
  but 
  two 
  particulars 
  did 
  this 
  paper 
  leave 
  

   anything 
  to 
  be 
  further 
  desired 
  ; 
  first, 
  the 
  specimens, 
  as 
  stated 
  

   in 
  the 
  paper, 
  were 
  of 
  weathered 
  material, 
  such 
  that 
  the 
  larger 
  

   minerals, 
  with 
  the 
  exception 
  of 
  a 
  few 
  small 
  cores 
  of 
  enstatite 
  

   had 
  to 
  be 
  determined 
  from 
  the 
  alteration 
  products 
  and 
  the 
  

   ground-mass 
  was 
  represented 
  by 
  a 
  mass 
  of 
  carbonates 
  and 
  ser- 
  

   pentine 
  ; 
  and, 
  second, 
  Dr. 
  Williams 
  was 
  unable 
  to 
  obtain, 
  either 
  

   from 
  his 
  own 
  collections 
  or 
  those 
  at 
  Hamilton 
  College, 
  the 
  

   "granitic" 
  and 
  "syenitic" 
  (or 
  micaceous 
  and 
  hornblenclic) 
  

   " 
  accretions," 
  mentioned 
  by 
  Yanuxem. 
  

  

  Somewhat 
  later 
  in 
  further 
  excavations, 
  additional 
  material 
  

   was 
  obtained, 
  on 
  which 
  a 
  brief 
  note 
  was 
  presented 
  to 
  the 
  Geo- 
  

   logical 
  Society 
  of 
  America, 
  at 
  JS 
  T 
  ew 
  York, 
  December, 
  1889.* 
  

   The 
  geological 
  relations 
  proving 
  the 
  intrusive 
  character, 
  are 
  

   set 
  forth, 
  and 
  the 
  general 
  statement 
  is 
  made 
  that 
  the 
  minerals 
  

   of 
  the 
  rock 
  are 
  not 
  all 
  altered 
  to 
  serpentine, 
  but 
  beyond 
  this, 
  

   no 
  further 
  determinations 
  are 
  recorded 
  than 
  were 
  given 
  in 
  the 
  

  

  * 
  Bulletin, 
  vol. 
  i, 
  p. 
  533. 
  

  

  