﻿./. 
  D. 
  Dana 
  — 
  Features 
  of 
  non-volcanic 
  Igneous 
  Ejections. 
  101 
  

  

  undetermined. 
  Exposures 
  that 
  will 
  afford 
  the 
  facts 
  are 
  most 
  

   likely 
  to 
  be 
  found 
  along 
  the 
  eastern 
  base 
  of 
  the 
  ridge. 
  At 
  one 
  

   place 
  where 
  the 
  surface 
  of 
  trap 
  had 
  been 
  uncovered 
  but 
  not 
  

   abraded, 
  which 
  was 
  seemingly 
  favorable 
  for 
  a 
  safe 
  conclusion, 
  

   the 
  slope 
  was 
  25° 
  to 
  30°, 
  and 
  suggested 
  the 
  angle 
  of 
  30° 
  for 
  

   the 
  inclination. 
  But 
  the 
  trap 
  at 
  the 
  place 
  may 
  have 
  been 
  part 
  

   of 
  the 
  outflow, 
  and 
  not 
  that 
  of 
  a 
  dike. 
  Observations 
  along 
  the 
  

   eastern 
  slope 
  of 
  the 
  range 
  farther 
  north 
  may 
  obtain 
  decisive 
  facts. 
  

  

  The 
  Outflow. 
  — 
  The 
  slopes 
  of 
  the 
  higher 
  parts 
  of 
  the 
  West 
  

   Rock 
  ridge, 
  the 
  pitch 
  of 
  the 
  columns 
  of 
  the 
  western 
  front, 
  and 
  

   the 
  resemblance 
  in 
  features 
  of 
  West 
  Rock 
  to 
  East 
  Rock, 
  lead 
  

   to 
  a 
  like 
  conclusion 
  for 
  the 
  two, 
  that 
  the 
  outflow 
  was 
  lacco- 
  

   lithic 
  ; 
  in 
  other 
  words, 
  that 
  the 
  liquid 
  rock 
  forced 
  its 
  way 
  

   between 
  layers 
  of 
  sandstone, 
  and 
  made 
  the 
  chamber 
  it 
  occu- 
  

   pied. 
  The 
  present 
  thickness 
  of 
  the 
  mass 
  is 
  nearly 
  250 
  feet. 
  

   The 
  overlying 
  sandstone 
  is 
  to 
  a 
  large 
  extent 
  the 
  weak, 
  chip- 
  

   making 
  rock 
  of 
  dark 
  red 
  and 
  purplish 
  color 
  already 
  described. 
  

   It 
  is 
  remarkable 
  that 
  a 
  rock 
  of 
  so 
  feeble 
  coherence 
  could 
  have 
  

   been 
  lifted 
  in 
  the 
  way 
  mentioned. 
  

  

  The 
  questions 
  suggested 
  by 
  East 
  Rock 
  here 
  come 
  up 
  again 
  : 
  

   Whether 
  the 
  feeble 
  slope 
  of 
  the 
  surface 
  from 
  the 
  west 
  edge 
  of 
  

   the 
  summit 
  eastward 
  to 
  the 
  300-foot 
  contour-line, 
  and 
  the 
  

   small 
  thickness 
  of 
  the 
  trap, 
  are 
  due 
  to 
  abrasion, 
  or 
  whether 
  the 
  

   present 
  conditions 
  are 
  nearly 
  those 
  of 
  the 
  original 
  outflow. 
  As 
  

   the 
  length 
  of 
  the 
  outflow 
  is 
  nearly 
  500 
  yards, 
  the 
  mass, 
  if 
  

   forced 
  up 
  between 
  layers 
  dipping. 
  25° 
  eastward, 
  would 
  have 
  

   had 
  a 
  much 
  larger 
  amount 
  to 
  lose 
  by 
  abrasion 
  than 
  in 
  the 
  case 
  

   of 
  East 
  Rock.* 
  Speculation 
  is 
  here 
  set 
  aside 
  by 
  the 
  actual 
  

   east-and-west 
  section 
  of 
  the 
  Rock 
  which 
  is 
  presented 
  along 
  

   its 
  southern 
  front, 
  and 
  is 
  shown 
  in 
  part 
  on 
  Plate 
  VII, 
  from 
  a 
  

   photograph. 
  f 
  It 
  exhibits 
  the 
  trap 
  resting, 
  to 
  the 
  eastward, 
  on 
  

  

  * 
  The 
  thickness 
  does 
  not 
  admit 
  of 
  calculation, 
  because 
  the 
  only 
  datum 
  besides 
  

   the 
  dip 
  of 
  the 
  sandstone, 
  is 
  the 
  height 
  of 
  the 
  bottom 
  of 
  the 
  trap 
  over 
  the 
  sand- 
  

   stone 
  on 
  the 
  west 
  front 
  (about 
  200 
  feet) 
  ; 
  the 
  height 
  of 
  the 
  outflow 
  where 
  it 
  left 
  

   the 
  fissure 
  is 
  not 
  ascertainable. 
  

  

  f 
  The 
  fine 
  photograph 
  was 
  taken 
  by 
  M. 
  W. 
  Filley, 
  of 
  the 
  firm 
  of 
  Bundy 
  & 
  Filley, 
  

   of 
  New 
  Haven. 
  The 
  sandstone 
  has 
  here 
  been 
  exposed 
  to 
  view 
  by 
  the 
  removal 
  

   of 
  the 
  debris 
  for 
  macadamizing. 
  The 
  irregular 
  line 
  in 
  the 
  plate 
  a 
  third 
  of 
  an 
  

   inch 
  above 
  the 
  sandstone 
  was 
  the 
  limit 
  of 
  the 
  talus 
  or 
  debris 
  slope 
  ; 
  and 
  the 
  

   line 
  below 
  the 
  sandstone 
  is 
  the 
  profile 
  of 
  the 
  quarry 
  wagon 
  road. 
  Along 
  the 
  

   part 
  of 
  the 
  section 
  represented, 
  the 
  height 
  of 
  this 
  road 
  is 
  ninety 
  to 
  one 
  hundred 
  

   feet. 
  If 
  the 
  debris 
  were 
  wholly 
  removed 
  to 
  the 
  bottom 
  of 
  the 
  slope, 
  the 
  height 
  

   of 
  the 
  sandstone 
  exposed 
  to 
  view 
  would 
  be, 
  where 
  greatest, 
  over 
  150 
  feet. 
  

  

  The 
  photograph 
  does 
  great 
  injustice 
  to 
  the 
  view 
  in 
  the 
  diminution 
  of 
  the 
  

   vertical 
  as 
  compared 
  with 
  the 
  horizontal 
  scale, 
  and 
  also 
  in 
  flattening 
  the 
  angle 
  of 
  

   dip 
  in 
  the 
  sandstone. 
  200 
  feet 
  measured 
  on 
  the 
  quarry 
  road 
  reaches 
  from 
  the 
  

   eastern 
  point 
  of 
  the 
  sandstone 
  section 
  westward 
  to 
  within 
  twenty-five 
  feet 
  of 
  the 
  

   line 
  of 
  the 
  deep 
  notch 
  in 
  the 
  columnar 
  front 
  of 
  the 
  Rock 
  (the 
  place 
  where 
  the 
  

   first 
  section 
  of 
  sandstone 
  ends); 
  but 
  this 
  length 
  applied 
  vertically 
  to 
  the 
  front 
  

   above 
  the 
  road 
  would 
  make 
  it 
  only 
  180 
  feet 
  in 
  height, 
  when 
  in 
  fact 
  this 
  

   height 
  where 
  greatest 
  is 
  over 
  300 
  feet. 
  This 
  error 
  arises 
  partly 
  from 
  the 
  fact 
  

   that 
  the 
  view 
  was 
  taken 
  from 
  the 
  terrace 
  opposite, 
  which 
  is 
  only 
  sixty 
  feet 
  high, 
  

   but 
  more 
  from 
  the 
  error 
  in 
  an 
  ordinary 
  lens. 
  

  

  