﻿J. 
  D. 
  Dana 
  — 
  PercivaVs 
  Map 
  of 
  the 
  Jura-Trias. 
  441 
  

  

  ridge 
  (Pond 
  ridge, 
  of 
  Percival) 
  on 
  the 
  west 
  side 
  of 
  Saltonstall 
  

   Lake. 
  To 
  the 
  north 
  of 
  this 
  ridge, 
  and 
  a 
  little 
  to 
  the 
  eastward, 
  

   is 
  another 
  bow-shaped 
  ridge, 
  the 
  Totoket 
  ; 
  and 
  the 
  line 
  of 
  

   these 
  two 
  ridges 
  is 
  continued 
  northward 
  by 
  other 
  high 
  trap- 
  

   ridges, 
  extending 
  along 
  the 
  western 
  borders 
  of 
  the 
  townships 
  

   of 
  Durham 
  and 
  Middletown 
  and 
  beyond 
  toward 
  Hartford. 
  

  

  In 
  the 
  metamorphic 
  region, 
  outside 
  of 
  the 
  Jura-Trias, 
  there 
  

   are 
  two 
  dikes, 
  one 
  on 
  the 
  east, 
  and 
  another 
  on 
  the 
  west. 
  They 
  

   are 
  referred 
  by 
  Percival 
  rightly 
  to 
  the 
  same 
  system 
  as 
  those 
  

   within 
  the 
  area. 
  That 
  on 
  the 
  west 
  is 
  the 
  "Buttress 
  Dike" 
  in 
  

   its 
  course 
  through 
  Woodbridge 
  and 
  Orange, 
  lettered 
  W. 
  1. 
  

   The 
  eastern 
  one 
  commences 
  in 
  Branford 
  and 
  is 
  continued 
  

   through 
  North 
  Branford, 
  where 
  it 
  is 
  lettered 
  3 
  E. 
  1., 
  and 
  

   northeastward, 
  as 
  mapped 
  by 
  Percival, 
  to 
  the 
  Massachusetts 
  

   line. 
  

  

  The 
  large 
  river 
  in 
  the 
  northeast 
  corner 
  of 
  the 
  map 
  is 
  the 
  

   Connecticut. 
  At 
  Hartford 
  its 
  course 
  becomes 
  changed 
  from 
  

   south-by-west 
  to 
  south 
  ; 
  and 
  at 
  Middletown 
  it 
  leaves 
  the 
  Jura- 
  

   Trias 
  area 
  and 
  goes 
  off 
  southeastward 
  to 
  the 
  Sound, 
  the 
  waters 
  

   having 
  been 
  forced 
  from 
  their 
  former 
  course 
  by 
  the 
  barrier 
  to 
  

   the 
  west 
  made 
  of 
  belts 
  of 
  trap 
  and 
  adjoining 
  hard 
  sandstone 
  — 
  an 
  

   event 
  which 
  took 
  place 
  whenever 
  this 
  trap 
  region 
  was 
  raised 
  

   above 
  the 
  sea-level. 
  The 
  valley 
  lying 
  to 
  the 
  west 
  of 
  the 
  Mt. 
  

   Tom 
  trap-range 
  contains 
  to 
  the 
  north 
  the 
  large 
  bend 
  of 
  the 
  

   Farmington 
  River; 
  the 
  left 
  side 
  of 
  the 
  bend 
  received 
  waters 
  

   from 
  the 
  northwest, 
  the 
  right 
  continues 
  the 
  flow 
  northeastward 
  

   to 
  the 
  Connecticut. 
  South 
  of 
  this 
  there 
  are 
  the 
  head-waters 
  of 
  

   the 
  Quinnipiac, 
  and 
  still 
  farther 
  south, 
  Neck 
  River, 
  the 
  stream 
  

   also 
  called 
  Mill 
  River. 
  

  

  The 
  southern 
  end 
  of 
  the 
  area, 
  as 
  is 
  shown 
  on 
  the 
  map, 
  nar- 
  

   rows 
  rather 
  abruptly, 
  owing 
  mainly 
  to 
  the 
  bending 
  westward 
  

   of 
  the 
  eastern 
  side. 
  While 
  the 
  width 
  is 
  eighteen 
  miles 
  in 
  the 
  

   latitude 
  of 
  Middletown, 
  it 
  is 
  hardly 
  two 
  at 
  the 
  entrance 
  to 
  

   New- 
  Haven 
  Bay, 
  the 
  southern 
  end 
  of 
  the 
  Jura-Trias 
  estuary. 
  

   The 
  granitoid 
  gneiss 
  of 
  the 
  eastern 
  shore 
  and 
  of 
  Light 
  House 
  

   Ledge 
  extends 
  to 
  within 
  two 
  miles 
  of 
  the 
  slaty 
  rocks 
  (chloritic 
  

   hydromica 
  schist) 
  of 
  the 
  western 
  cape, 
  or 
  Savin 
  Rock 
  ;* 
  and 
  as 
  

   the 
  depth 
  off 
  the 
  latter 
  cape 
  is 
  but 
  a 
  few 
  feet 
  and 
  over 
  sands 
  

   for 
  a 
  long 
  distance 
  out, 
  the 
  actual 
  wi'dth 
  of 
  the 
  interval 
  may 
  

   not 
  be 
  more 
  than 
  a 
  mile 
  and 
  a 
  half. 
  The 
  outline 
  on 
  the 
  east 
  

   is 
  followed 
  closely 
  by 
  the 
  easternmost 
  trap-dike, 
  showing, 
  ap- 
  

   parently, 
  that 
  the 
  narrowing 
  is 
  a 
  fundamental 
  feature 
  of 
  the 
  

  

  * 
  The 
  granite 
  and 
  gneiss 
  of 
  the 
  eastern 
  Cape 
  are 
  probably 
  Archasan, 
  and 
  the 
  

   hydromica 
  schist 
  of 
  the 
  western 
  side 
  with 
  the 
  feebly 
  crystalline 
  limestone 
  which 
  

   occurs 
  in 
  it, 
  and 
  with 
  other 
  schists 
  to 
  the 
  west, 
  may 
  be 
  early 
  Paleozoic. 
  

  

  