﻿1 
  

  

  442 
  J. 
  D. 
  Dana 
  — 
  The 
  Upturning 
  of 
  

  

  area, 
  and 
  not 
  one 
  due 
  to 
  a 
  subsequent 
  uplifting 
  of 
  the 
  coast- 
  

   region 
  and 
  its 
  denudation. 
  This 
  narrow 
  channel 
  at 
  the 
  end 
  is 
  

   the 
  more 
  remarkable 
  in 
  view 
  of 
  the 
  fact 
  that 
  only 
  live 
  miles 
  

   north 
  of 
  the 
  outcropping 
  granite 
  of 
  the 
  shore, 
  the 
  sandstone, 
  

   — 
  as 
  the 
  recent 
  condition 
  of 
  the 
  boring 
  at 
  the 
  Winchester 
  Re- 
  

   peating 
  Arms 
  Factory 
  shows 
  — 
  extends 
  to 
  a 
  depth 
  below 
  the 
  

   sea-level 
  of 
  at 
  least 
  3,100 
  feet. 
  The 
  metamorphic 
  rocks 
  of 
  the 
  

   hills 
  to 
  the 
  west 
  are 
  only 
  two 
  miles 
  distant, 
  and 
  hence 
  that 
  side 
  

   of 
  the 
  trough 
  has 
  a 
  mean 
  pitch 
  of 
  1 
  : 
  3J, 
  or 
  about 
  Yl\ 
  degrees, 
  

   but 
  much 
  larger 
  than 
  this, 
  probably 
  in 
  the 
  western 
  or 
  outer 
  of 
  

   the 
  two 
  miles, 
  and 
  smaller 
  in 
  the 
  inner. 
  The 
  southern 
  extrem- 
  

   ity 
  of 
  the 
  Jura-Trias 
  trough 
  or 
  geosyncline 
  has, 
  hence, 
  some- 
  

   thing 
  of 
  the 
  shape 
  of 
  the 
  prow 
  end 
  of 
  a 
  boat. 
  

  

  These 
  facts 
  seem 
  to 
  prove 
  that 
  the 
  Jura-Trias 
  trough, 
  or 
  at 
  

   least 
  its 
  lower 
  3,100 
  feet, 
  did 
  not 
  extend 
  out 
  into 
  the 
  Sound 
  

   but 
  had 
  its 
  termination 
  in 
  what 
  is 
  now 
  New 
  Haven 
  Bay. 
  

  

  For 
  explanations 
  of 
  the 
  lettering 
  on 
  Percival's 
  map 
  and 
  

   other 
  details, 
  reference 
  must 
  be 
  had 
  to 
  his 
  Geological 
  Report. 
  

   The 
  scale 
  of 
  the 
  map 
  is 
  nine-tenths 
  of 
  an 
  inch 
  to 
  five 
  miles. 
  

  

  The 
  uplifts, 
  whether 
  before 
  or 
  after 
  the 
  trap 
  ejections. 
  

  

  Is 
  the 
  West 
  Rock 
  trap-range 
  in 
  which 
  the 
  uplifting 
  preceded 
  

   beyond 
  question 
  the 
  eruption, 
  typical 
  for 
  all 
  the 
  north-and-south 
  

   trap-ranges? 
  The 
  form 
  of 
  the 
  trap-belt 
  on 
  the 
  map 
  is 
  strik- 
  

   ingly 
  like 
  that 
  of 
  other 
  trap-ranges 
  in 
  the 
  valley, 
  in 
  the 
  little 
  

   width 
  of 
  its 
  outcrop, 
  in 
  the 
  composite 
  character 
  of 
  the 
  belt, 
  in 
  

   its 
  hooked 
  extremity, 
  in 
  the 
  curvature 
  and 
  overlapping 
  feature 
  

   of 
  the 
  parts, 
  and 
  in 
  its 
  gradual 
  disappearance 
  seventeen 
  miles 
  

   to 
  the 
  north 
  just 
  west 
  of 
  where 
  another 
  greater 
  range 
  — 
  the 
  

   Mt. 
  Tom 
  Range 
  begins. 
  The 
  fact 
  that 
  this 
  western 
  range 
  was 
  

   erupted 
  after 
  the 
  upturning 
  of 
  the 
  sandstone 
  affords 
  hence 
  

   some 
  reason 
  for 
  suspecting 
  that 
  this 
  was 
  true 
  also 
  of 
  the 
  rest 
  

   of 
  the 
  trap 
  in 
  the 
  system 
  of 
  ridges. 
  

  

  In 
  East 
  Haven, 
  east 
  of 
  New 
  Haven, 
  the 
  first 
  trap-ridge 
  west 
  

   of 
  Saltonstall 
  Lake 
  afforded, 
  at 
  its 
  southern 
  end, 
  the 
  section 
  on 
  

   page 
  104, 
  proving 
  that 
  this 
  belt 
  also, 
  like 
  that 
  of 
  West 
  Rock, 
  

   was 
  erupted 
  after 
  the 
  upturning 
  of 
  the 
  sandstone. 
  This 
  ridge 
  

   is 
  only 
  500 
  yards 
  west 
  of 
  the 
  Saltonstall 
  Ridge, 
  and 
  it 
  may 
  be 
  

   reasonably 
  believed 
  that 
  the 
  bow-shaped 
  ridge 
  was 
  also 
  an 
  

   outflow 
  after 
  the 
  upturning. 
  This 
  conclusion 
  is 
  sustained 
  by 
  

   the 
  further 
  fact 
  that 
  the 
  third 
  example 
  of 
  trap 
  overlying 
  up- 
  

   turned 
  sandstone 
  mentioned 
  on 
  page 
  105, 
  stands 
  directly 
  to 
  the 
  

   east 
  and 
  only 
  3000 
  yards 
  away. 
  Moreover 
  Dr. 
  E. 
  O. 
  Hovey, 
  in 
  

   his 
  paper 
  already 
  referred 
  to, 
  makes 
  the 
  trap 
  of 
  Saltonstall 
  

   ridge 
  intrusive 
  ; 
  and 
  the 
  conclusion, 
  according 
  to 
  my 
  own 
  

   examination 
  with 
  him 
  of 
  his 
  facts, 
  I 
  believe 
  to 
  be 
  right. 
  

  

  