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  CONTRIBUTIONS 
  TO 
  THE 
  GEOLOGY 
  OF 
  

  

  of 
  carbonate 
  of 
  lime. 
  It 
  appears 
  to 
  consist 
  of 
  silex, 
  slightly 
  tinged 
  

   with 
  oxide 
  of 
  iron 
  ; 
  approaching 
  in 
  its 
  porous 
  character 
  and 
  harsh 
  gritty 
  

   texture 
  to 
  the 
  nature 
  of 
  the 
  burr-stone 
  of 
  France. 
  Associated 
  with 
  

   this 
  is 
  a 
  more 
  compact 
  rock, 
  containing 
  some 
  carbonate 
  of 
  lime, 
  

   with 
  much 
  silex, 
  and 
  exhibiting 
  very 
  perfect 
  casts 
  and 
  impressions 
  of 
  

   Pectens, 
  Cardium, 
  &c. 
  Over 
  these 
  strata 
  is 
  the 
  usual 
  layer 
  of 
  iron- 
  

   stone, 
  and 
  the 
  general 
  aspect 
  of 
  the 
  upper 
  beds 
  is 
  somewhat 
  ferrugi- 
  

   nous. 
  

  

  20. 
  It 
  is 
  interesting 
  to 
  remark 
  that, 
  with 
  some 
  interruptions, 
  a 
  frag- 
  

   mentary 
  deposit 
  similar 
  to 
  that 
  observed 
  at 
  York 
  extends 
  to 
  the 
  lower 
  

   extremity 
  of 
  the 
  peninsula. 
  At 
  Pocosin, 
  a 
  flat 
  swampy 
  country, 
  which 
  

   is 
  often 
  inundated 
  by 
  the 
  tides, 
  this 
  deposit 
  is 
  uniformly 
  met 
  with 
  by 
  

   digging 
  a 
  few 
  feet 
  below 
  the 
  surface. 
  Pectunculus, 
  Pecten, 
  Ostrea, 
  as 
  

   well 
  as 
  numerous 
  small 
  shells, 
  occur 
  mingled 
  with 
  it, 
  as 
  at 
  York 
  ; 
  the 
  

   fragments, 
  however, 
  are 
  not 
  cemented 
  together, 
  but 
  form 
  a 
  loose 
  fria- 
  

   ble 
  mass. 
  

  

  21. 
  A 
  very 
  interesting 
  feature 
  in 
  the 
  structure 
  of 
  the 
  cliff 
  at 
  York 
  

   remains 
  to 
  be 
  described. 
  Though 
  the 
  general 
  direction 
  of 
  the 
  fossil 
  

   beds 
  is 
  nearly 
  horizontal, 
  several 
  of 
  the 
  strata 
  of 
  rock 
  are 
  composed 
  of 
  

   transverse 
  layers 
  parallel 
  to 
  each 
  other, 
  generally 
  dipping 
  towards 
  the 
  

   north, 
  and 
  making 
  an 
  angle 
  of 
  fifteen 
  or 
  twenty 
  degrees 
  with 
  the 
  hori- 
  

   zon. 
  The 
  course 
  of 
  these 
  laminae 
  sometimes 
  differs 
  in 
  adjoining 
  strata, 
  

   and 
  in 
  some 
  places 
  the 
  obliquity 
  diminishes 
  gradually 
  until 
  the 
  laminae 
  

   become 
  horizontal; 
  thus 
  presenting 
  a 
  remarkable 
  resemblance 
  to 
  the 
  

   appearances 
  described 
  by 
  Lyell 
  and 
  others 
  as 
  existing 
  in 
  the 
  Crag 
  of 
  

   England. 
  The 
  phenomenon 
  here 
  described, 
  viewed 
  in 
  connexion 
  with 
  

   the 
  fragmentary 
  structure 
  of 
  the 
  rock, 
  and 
  the 
  general 
  distribution 
  of 
  

   broken 
  shells 
  over 
  the 
  lower 
  extremity 
  of 
  the 
  peninsula, 
  would 
  seem 
  to 
  

   indicate 
  the 
  former 
  agency 
  in 
  this 
  district 
  of 
  coast 
  currents 
  and 
  an 
  

   ocean 
  surf. 
  

  

  22. 
  At 
  Burwell's 
  Mill, 
  and 
  other 
  localities 
  in 
  the 
  immediate 
  neigh- 
  

   bourhood 
  of 
  Williamsburg, 
  nearly 
  the 
  same 
  fossils 
  occur 
  as 
  at 
  King's 
  

   Mill 
  and 
  Yorktown. 
  Besides 
  shells 
  and 
  Zoophytes, 
  in 
  these 
  and 
  other 
  

   places 
  in 
  the 
  peninsula, 
  the 
  bones 
  of 
  cetaceous 
  animals 
  and 
  the 
  teeth 
  

   of 
  sharks 
  are 
  of 
  very 
  frequent 
  occurrence 
  in 
  the 
  fossiliferous 
  beds, 
  but 
  

   no 
  remains 
  of 
  fresh 
  water 
  or 
  land 
  animals 
  have 
  as 
  yet 
  been 
  discovered. 
  

  

  