﻿J. 
  D. 
  Dana 
  — 
  Features 
  of 
  non- 
  volcanic 
  Igneous 
  Ejections, 
  91 
  

  

  denudation 
  by 
  the 
  sea, 
  rivers 
  and 
  ice, 
  it 
  has 
  lost 
  all 
  of 
  the 
  

   sandstone 
  formation 
  that 
  may 
  have 
  covered 
  the 
  summit, 
  and 
  

   for 
  the 
  most 
  part 
  that 
  over 
  its 
  slopes 
  above 
  the 
  200-foot 
  con- 
  

   tour-line. 
  The 
  form 
  of 
  its 
  upper 
  portion 
  is 
  therefore 
  largely 
  

   that 
  of 
  the 
  trap 
  in 
  its 
  constitution 
  — 
  the 
  hard 
  rock 
  that 
  was 
  

   most 
  successful 
  in 
  resisting 
  wear. 
  This 
  fact 
  gives 
  special 
  

   interest 
  to 
  the 
  larger 
  and 
  more 
  detailed 
  topographical 
  map 
  

   making 
  Plate 
  III, 
  as 
  will 
  appear 
  beyond.* 
  

  

  To 
  the 
  north 
  is 
  Whitney 
  Peak, 
  which 
  has 
  already 
  been 
  

   described 
  as 
  the 
  eastern 
  extremity 
  of 
  the 
  Mill 
  Pock 
  series. 
  

   South 
  of 
  this 
  and 
  of 
  a 
  large 
  area 
  of 
  sandstone, 
  are 
  East 
  Pock 
  

   and 
  Indian 
  Head, 
  one 
  in 
  trap 
  surface, 
  but 
  in 
  fact 
  the 
  result 
  of 
  

   two 
  independent 
  outflows. 
  To 
  the 
  south 
  of 
  Indian 
  Head 
  is 
  

   Snake 
  Pock, 
  which 
  also 
  has 
  its 
  large 
  trap 
  mass, 
  but 
  is 
  peculiar 
  

   in 
  having 
  ridges 
  of 
  hard-baked 
  sandstone 
  that 
  are 
  higher 
  than 
  

   those 
  of 
  trap. 
  The 
  East 
  Pock 
  areas 
  of 
  trap 
  here 
  referred 
  to 
  

   are 
  lettered 
  on 
  the 
  map 
  BB', 
  CC'C", 
  DD'. 
  Besides 
  these 
  

   there 
  is 
  a 
  more 
  northern 
  one, 
  lettered 
  AA', 
  which 
  lies 
  near 
  the 
  

   eastern 
  foot 
  of 
  Whitney 
  Peak. 
  

  

  The 
  trap-mass 
  AA' 
  . 
  — 
  This 
  northernmost 
  mass, 
  is 
  about 
  one 
  

   hundred 
  yards 
  long. 
  At 
  its 
  northern 
  end 
  it 
  is 
  only 
  forty 
  feet 
  

   distant 
  from 
  the 
  tra]3 
  of 
  Whitney 
  Peak, 
  and 
  it 
  is 
  a 
  question, 
  

   therefore, 
  whether 
  it 
  is 
  not 
  a 
  part 
  of 
  the 
  latter 
  dike. 
  But 
  it 
  

   is 
  separated 
  from 
  it 
  by 
  outcropping 
  sandstone, 
  except 
  where 
  

   the 
  interval 
  is 
  narrowest, 
  and 
  at 
  this 
  point 
  there 
  was 
  until 
  

   recently 
  drained, 
  a 
  standing 
  pool 
  of 
  water, 
  a 
  pretty 
  good 
  indi- 
  

   cation 
  that 
  sandstone 
  exists 
  beneath, 
  since 
  trap 
  is 
  commonly 
  

   too 
  much 
  fissured 
  to 
  hold 
  water 
  or 
  afford 
  springs. 
  Moreover, 
  

   the 
  mass 
  AA' 
  has 
  the 
  trend 
  of 
  the 
  East 
  Pock 
  series; 
  and, 
  

  

  * 
  The 
  map 
  of 
  East 
  Rock 
  Park 
  which 
  is 
  the 
  hasis 
  of 
  Plate 
  III. 
  was 
  obtained 
  

   from 
  the 
  Engineer 
  department 
  in 
  Xew 
  Haven, 
  through 
  the 
  City 
  Engineer, 
  Mr. 
  

   A. 
  B. 
  Hill. 
  The 
  roads 
  of 
  the 
  Park 
  from 
  the 
  termination 
  of 
  Orange 
  St.. 
  around 
  by 
  

   the 
  north 
  to 
  the 
  summit 
  of 
  East 
  Rock 
  are 
  lettered 
  F. 
  and 
  the 
  others 
  E. 
  These 
  

   letters 
  refer 
  to 
  two 
  citizens 
  of 
  New 
  Haven. 
  Henry 
  Earnam 
  and 
  James 
  E. 
  English, 
  

   who 
  liberally 
  bore 
  the 
  expense 
  of 
  their 
  construction. 
  The 
  topography 
  is 
  in 
  part 
  

   from 
  the 
  Bache 
  Coast 
  Survey 
  map 
  : 
  but 
  the 
  accuracy 
  of 
  its 
  contour 
  lines 
  was 
  not 
  

   sufficient 
  for 
  their 
  transfer 
  to 
  the 
  Park 
  map. 
  The 
  heights 
  are 
  reckoned 
  from 
  

   bigh 
  tide. 
  The 
  map 
  is 
  indebted 
  to 
  Prof. 
  S. 
  E. 
  Barney, 
  for 
  the 
  determination 
  by 
  

   leveling 
  of 
  .the 
  height 
  of 
  the 
  highest 
  point 
  of 
  East 
  Rock, 
  just 
  south 
  of 
  the 
  monu- 
  

   ment 
  (358| 
  feet) 
  and 
  also 
  of 
  other 
  points 
  on 
  its 
  south 
  and 
  east 
  sides, 
  and 
  for 
  that 
  

   of 
  the 
  junction 
  of 
  the 
  trap 
  and 
  sandstone 
  on 
  the 
  west 
  front 
  near 
  Orange 
  St. 
  bridge 
  

   (155 
  feet). 
  The 
  height 
  of 
  the 
  bolt 
  at 
  the 
  Coast 
  Survey 
  Station 
  he 
  found 
  to 
  be 
  

   343 
  feet, 
  and 
  the 
  height 
  of 
  the 
  top 
  of 
  the 
  first 
  step 
  leading 
  to 
  the 
  terrace 
  about 
  

   the 
  monument, 
  355 
  feet. 
  (Prof. 
  Barney's 
  figures 
  are 
  underscored 
  on 
  the 
  map). 
  

   The 
  circuit 
  road 
  about 
  the 
  summit 
  has 
  a 
  height 
  of 
  320 
  to 
  350 
  feet: 
  and 
  the 
  nearly 
  

   parallel 
  road 
  on 
  the 
  east 
  rises 
  from 
  about 
  216 
  feet 
  near 
  the 
  quarries 
  south 
  of 
  the 
  sum- 
  

   mit, 
  to 
  270 
  near 
  the 
  junction 
  of 
  the 
  •' 
  Earnam 
  drive" 
  and 
  "English 
  drive," 
  and 
  thence 
  

   declines 
  northward 
  to 
  about 
  250 
  where 
  it 
  bends 
  westward. 
  The 
  letters 
  S 
  on 
  the 
  

   map 
  indicate 
  an 
  outcrop 
  of 
  sandstone 
  in 
  the 
  vicinity 
  of 
  junctions 
  with 
  the 
  trap. 
  

  

  In 
  giving 
  the 
  topography 
  of 
  the 
  Rock, 
  the 
  quarry 
  excavations 
  on 
  the 
  south 
  

   side 
  above 
  a 
  level 
  of 
  216 
  feet 
  are 
  not 
  introduced, 
  it 
  seeming 
  best 
  to 
  represent 
  the 
  

   Rock 
  in 
  its 
  original 
  form. 
  They 
  are 
  separately 
  mapped 
  on 
  the 
  plate. 
  

  

  