﻿362 
  JOURNAL 
  OF 
  THK 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOL. 
  12, 
  NO. 
  15 
  

  

  composed 
  of 
  an 
  igneous 
  complex 
  of 
  plutonic 
  rocks 
  and 
  old 
  sediments 
  

   among 
  which 
  there 
  are 
  no 
  greenstone 
  schists. 
  The 
  pre-Cambrian, 
  

   however 
  contains 
  conspicuous 
  veins 
  of 
  glassy 
  blue 
  quartz, 
  pebbles 
  of 
  

   which 
  are 
  inclosed 
  in 
  the 
  basal 
  Cambrian 
  sediments. 
  The 
  conglom- 
  

   erate 
  is 
  well 
  exposed 
  near 
  the 
  sand 
  mines 
  northwest 
  of 
  Honeybrook, 
  

   where 
  it 
  is 
  only 
  150 
  feet 
  thick. 
  

  

  In 
  Welsh 
  Mountain 
  the 
  lower 
  part 
  of 
  the 
  quartzite 
  above 
  the 
  con- 
  

   glomerate 
  is 
  vitreous 
  and 
  the 
  upper 
  part 
  is 
  granular, 
  both 
  carrying 
  

   Scolithus 
  tubes. 
  The 
  granular 
  quartzite 
  is 
  generally 
  disintegrated 
  

   at 
  the 
  surface 
  and 
  is 
  quarried 
  for 
  sand. 
  It 
  passes 
  upward 
  into 
  a 
  fine- 
  

   grained, 
  white, 
  siliceous, 
  laminated 
  clay, 
  which 
  is 
  also 
  mined. 
  Four 
  

   hundred 
  feet 
  of 
  the 
  formation 
  has 
  been 
  measured 
  in 
  quarries 
  and 
  other 
  

   good 
  exposures. 
  The 
  Harpers 
  phyllite, 
  estimated 
  to 
  be 
  about 
  1,500 
  

   feet 
  thick, 
  is 
  composed 
  of 
  gray 
  sandy 
  phyllite. 
  At 
  the 
  top 
  the 
  phyllite 
  

   is 
  interbedded 
  with 
  light 
  gray, 
  granular 
  quartzite 
  which 
  weathers 
  

   to 
  a 
  porous 
  rusty 
  rock 
  containing 
  molds 
  of 
  Obolella 
  and 
  trilobite 
  frag- 
  

   ments. 
  About 
  150 
  feet 
  of 
  the 
  upper 
  quartzose 
  beds 
  are 
  probably 
  

   equivalent 
  to 
  the 
  Antietam 
  sandstone 
  of 
  South 
  Mountain. 
  

  

  The 
  arenaceous 
  series 
  of 
  the 
  Hellam-Chickies 
  and 
  the 
  Welsh 
  Mountain 
  

   anticlines 
  is 
  overlain 
  by 
  the 
  limestones 
  of 
  Lancaster 
  Valley. 
  The 
  

   Vintage 
  dolomite, 
  the 
  oldest 
  of 
  these 
  limestones, 
  is 
  in 
  part 
  a 
  gray, 
  

   heavy-bedded 
  dolomite, 
  which 
  weathers 
  to 
  a 
  whitish 
  chalky 
  surface, 
  

   and 
  in 
  part 
  a 
  knotty, 
  dark 
  blue 
  dolomite 
  with 
  argillaceous 
  partings. 
  

   Some 
  of 
  the 
  beds 
  are 
  sparkling, 
  gray 
  to 
  blue 
  mottled, 
  with 
  siliceous 
  

   and 
  calcareous 
  blebs 
  that 
  stand 
  in 
  relief 
  on 
  the 
  weathered 
  surfaces. 
  

   At 
  the 
  base 
  is 
  a 
  whitish, 
  schistose, 
  thin-bedded 
  impure 
  dolomite 
  con- 
  

   taining 
  muscovite 
  flakes. 
  This 
  formation 
  closely 
  resembles 
  the 
  Toms- 
  

   town 
  dolomite 
  on 
  the 
  northwest 
  flanks 
  of 
  South 
  Mountain. 
  It, 
  

   however, 
  is 
  known 
  to 
  represent 
  only 
  a 
  part 
  of 
  the 
  Tomstown 
  dolomite 
  

   and 
  is 
  therefore 
  named 
  Vintage 
  dolomite 
  from 
  the 
  small 
  village 
  15 
  

   miles 
  east 
  of 
  Lancaster, 
  where 
  most 
  of 
  it 
  the 
  section 
  excellently 
  ex- 
  

   posed 
  in 
  a 
  cut 
  of 
  the 
  Pennsylvania 
  Railroad. 
  

  

  The 
  Kinzers 
  formation 
  which 
  overlies 
  the 
  Vintage 
  is 
  best 
  exposed 
  

   in 
  the 
  Pennsylvania 
  Railroad 
  cut 
  at 
  Kinzers 
  just 
  east 
  of 
  Vintage. 
  

   At 
  the 
  base 
  there 
  are 
  a 
  few 
  thin 
  beds 
  of 
  impure 
  dolomite 
  that 
  weather 
  

   to 
  an 
  earthy 
  tripoli, 
  containing 
  at 
  many 
  places 
  remains 
  of 
  Salterella, 
  

   brachiopods, 
  and 
  trilobites. 
  These 
  beds 
  are 
  followed 
  by 
  a 
  variable 
  

   thickness 
  of 
  blue 
  hackly 
  shale 
  as 
  much 
  as 
  50 
  feet 
  thick 
  in 
  places. 
  

   Northwest 
  of 
  Lancaster 
  this 
  shale 
  carries 
  abundant 
  trilobites 
  chiefly 
  

   Olenellus, 
  described 
  by 
  Walcott 
  and 
  extensively 
  collected 
  by 
  Professor 
  

  

  