﻿I08 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  is 
  of 
  the 
  type 
  of 
  the 
  cross-bedding 
  structure 
  in 
  sandstone. 
  Such 
  

   structure 
  indicates 
  that 
  the 
  bed 
  possessing 
  it 
  was 
  a 
  fine 
  calcareous 
  

   sand, 
  subject 
  to 
  shifting 
  movements 
  by 
  waves 
  and 
  deposited 
  in 
  

   moderately 
  shallow 
  water. 
  We 
  need 
  look 
  for 
  organic 
  remains 
  in 
  

   such 
  a 
  rock 
  with 
  no 
  more 
  assurance 
  of 
  finding 
  them 
  than 
  we 
  bring 
  

   to 
  the 
  examination 
  of 
  uniform 
  bedded 
  shales. 
  They 
  may 
  be 
  abun- 
  

   dant 
  or 
  they 
  may 
  be 
  rare 
  or 
  absent 
  altogether. 
  Thus 
  a 
  Hmestone 
  

   need 
  not 
  be 
  necessarily 
  a 
  fossiliferous 
  rock. 
  

  

  Geodes 
  of 
  the 
  usual 
  type 
  are 
  common, 
  the 
  dolomitic 
  lining 
  pre- 
  

   dominating. 
  

  

  7) 
  On 
  the 
  preceding 
  thin 
  stratum 
  follows 
  a 
  limestone 
  mass 
  of 
  very 
  

   uniform 
  character^ 
  hardly 
  separable 
  into 
  district 
  strata, 
  though 
  con- 
  

   sisting 
  of 
  numerous 
  beds.^ 
  27 
  feet 
  of 
  this 
  stratum 
  are 
  shown 
  at 
  the 
  

   quarry 
  near 
  the 
  northern 
  end 
  of 
  the 
  section,' 
  where 
  the 
  upper 
  ex- 
  

   posed 
  bed 
  forms 
  the 
  surface 
  rock 
  of 
  the 
  plateau 
  above. 
  The 
  beds 
  

   are 
  generally 
  of 
  considerable 
  thickness, 
  but 
  the 
  fine 
  stratification 
  

   structure 
  is 
  not 
  so 
  well 
  marked 
  as 
  in 
  the 
  strata 
  below. 
  The 
  rock 
  

   may 
  be 
  considered 
  a 
  compact 
  granular 
  dolomite, 
  in 
  which 
  consider- 
  

   able 
  change 
  has 
  taken 
  place 
  since 
  its 
  original 
  deposition. 
  It 
  is 
  of 
  a 
  

   grayish 
  color 
  but 
  weathers 
  to 
  a 
  lighter 
  tint. 
  Geodes 
  are 
  plentiful, 
  

   often 
  quite 
  large, 
  and 
  in 
  these, 
  minerals 
  of 
  great 
  beauty 
  are 
  not 
  infre- 
  

   quently 
  found. 
  The 
  most 
  common 
  are 
  the 
  snowy 
  variety 
  of 
  gyp- 
  

   sum 
  or 
  alabaster, 
  the 
  darker 
  gray, 
  massive, 
  fine 
  anhydrite 
  and 
  the 
  

   uniform, 
  fine, 
  dolomite 
  rhombohedra 
  with 
  curved 
  faces, 
  generally 
  of 
  

   a 
  pinkish 
  tint 
  and 
  familiarly 
  known 
  as 
  pearl 
  spar. 
  Long 
  slender 
  

   crystals 
  of 
  calcite, 
  generally 
  in 
  the 
  form 
  known 
  as 
  scalenohedra, 
  or 
  

   dogtooth 
  spar, 
  are 
  not 
  uncommon. 
  These 
  are 
  commonly 
  of 
  a 
  

   golden 
  color, 
  and 
  large 
  enough 
  to 
  show 
  well 
  their 
  crystal 
  faces. 
  In 
  

   the 
  new 
  power 
  tunnel 
  which 
  was 
  excavated 
  in 
  the 
  neighborhood 
  of 
  

   the 
  falls, 
  large 
  masses 
  of 
  transparent 
  gypsum 
  of 
  the 
  selenite 
  variety 
  

   were 
  found 
  in 
  cavities 
  in 
  this 
  rock. 
  Some 
  of 
  these 
  pieces 
  were 
  6 
  

   inches 
  in 
  length. 
  Masses 
  of 
  limestone 
  lined 
  with 
  pinkish 
  dolomite 
  

   crystals 
  and 
  occasional 
  large 
  masses 
  of 
  silvery 
  selenite, 
  and 
  set 
  with 
  

  

  ^The 
  distinction 
  between 
  stratum 
  and 
  bed 
  is 
  an 
  important 
  one. 
  A 
  stratum 
  

   is 
  a 
  rock 
  mass 
  having 
  throughout 
  the 
  same 
  lithic 
  character, 
  and 
  may 
  be 
  

   thick 
  or 
  thin. 
  A 
  bed, 
  on 
  the 
  other 
  hand, 
  is 
  that 
  portion 
  of 
  a 
  stratum 
  limited 
  

   by 
  horizontal 
  separation 
  planes. 
  See 
  Geology 
  and 
  paleontology 
  of 
  Eighteen 
  

   Mile 
  creek 
  pt 
  i. 
  Introduction. 
  

  

  