﻿the 
  Connecticut 
  Valley 
  Sandstone. 
  445 
  

  

  the 
  side 
  of 
  the 
  direction 
  of 
  dip. 
  In 
  case 
  . 
  the 
  compression 
  

   varied 
  at 
  different 
  depths, 
  diminishing 
  downwards, 
  a 
  shearing 
  

   force 
  wonld 
  be 
  introduced, 
  by 
  which 
  the 
  slabs 
  could 
  be 
  

   thrown 
  over 
  past 
  the 
  vertical."* 
  Accordingly, 
  his 
  figure 
  rep- 
  

   resents 
  the 
  sandstone 
  overlying 
  the 
  inclined 
  upper 
  surfaces 
  of 
  

   the 
  successive 
  slabs 
  or 
  blocks, 
  and 
  as 
  deriving 
  in 
  this 
  way 
  its 
  

   eastward 
  dip. 
  The 
  fault-planes, 
  it 
  will 
  be 
  understood, 
  are 
  not 
  

   those 
  of 
  the 
  fissures 
  that 
  supply 
  the 
  trap 
  ; 
  for 
  in 
  his 
  view 
  the 
  

   trap 
  and 
  sandstone 
  were 
  in 
  alternating 
  sheets 
  before 
  the 
  up- 
  

   turning 
  took 
  place. 
  These 
  fault-planes 
  are 
  nowhere 
  open 
  to 
  

   view, 
  and 
  hence 
  the 
  idea 
  has 
  not 
  been 
  sustained 
  by 
  actual 
  

   comparisons. 
  It 
  is 
  presented 
  by 
  Prof. 
  Davis 
  simply 
  as 
  an 
  

   hypothesis 
  for 
  future 
  consideration. 
  

  

  Assuming 
  with 
  him, 
  as 
  we 
  may 
  safely, 
  that 
  the 
  dip 
  of 
  the 
  

   fault-planes 
  is 
  eastward, 
  I 
  mentioned 
  in 
  my 
  former 
  paper 
  as 
  

   an 
  exception 
  to 
  the 
  hypothesis, 
  a 
  want 
  of 
  correspondence 
  be- 
  

   tween 
  the 
  strike 
  of 
  the 
  West 
  Rock 
  dike 
  and 
  other 
  dikes 
  near 
  

   ~New 
  Haven 
  and 
  that 
  of 
  the 
  schists 
  within 
  a 
  mile 
  to 
  the 
  west- 
  

   ward 
  of 
  West 
  Rock, 
  confining 
  my 
  statement 
  of 
  facts 
  to 
  those 
  

   of 
  the 
  New 
  Haven 
  region. 
  This 
  objection 
  is 
  not 
  cpiite 
  appo- 
  

   site, 
  since 
  the 
  comparison 
  is 
  made 
  with 
  the 
  direction, 
  of 
  trap- 
  

   dikes 
  and 
  not 
  with 
  the 
  strike 
  of 
  the 
  sandstone 
  which 
  most 
  

   nearly 
  represents 
  that 
  of 
  the 
  fault-planes. 
  I 
  now. 
  mention 
  

   other 
  facts 
  bearing 
  on 
  the 
  question. 
  West 
  of 
  the 
  JSTew 
  Haven 
  

   region, 
  along 
  a 
  line 
  through 
  Orange 
  and 
  Birmingham 
  sixteen 
  

   miles 
  long, 
  there 
  are 
  five 
  changes 
  between 
  eastward 
  and 
  west- 
  

   ward 
  in 
  the 
  dip 
  of 
  the 
  metamorphic 
  schists, 
  and 
  in 
  the 
  course 
  of 
  

   them 
  there 
  are 
  variations 
  in 
  the 
  dip 
  from 
  horizontal 
  to 
  vertical. 
  

   The 
  last 
  of 
  the 
  iive 
  is 
  a 
  case 
  in 
  which 
  a 
  broad 
  and 
  low 
  anti- 
  

   clinal, 
  consisting 
  of 
  coarse 
  gneiss 
  and 
  mica 
  schist 
  with 
  a 
  bed 
  

   of 
  crystalline 
  limestone, 
  has 
  the 
  beds 
  for 
  a 
  long 
  distance 
  near- 
  

   ly 
  horizontal. 
  As 
  the 
  mean 
  width 
  of 
  the 
  Jura-Trias 
  area 
  in 
  

   Connecticut 
  is 
  twenty 
  miles, 
  there 
  is 
  therefore 
  room 
  for 
  

   equally 
  large 
  variations 
  in 
  the 
  clip 
  of 
  the 
  crystalline 
  schists 
  

   beneath 
  it. 
  Again, 
  in 
  Berkshire 
  county, 
  Massachusetts, 
  as 
  well 
  

   as 
  to 
  the 
  north 
  and 
  south, 
  among 
  the 
  metamorphic 
  rocks 
  of 
  

   the 
  earlier 
  Paleozoic, 
  or 
  Taconic, 
  series, 
  the 
  dips 
  vary 
  from 
  

   east 
  to 
  west, 
  and 
  from 
  zero 
  to 
  90 
  degrees. 
  Such 
  facts, 
  however 
  

   exceptional, 
  make 
  it 
  necessary 
  to 
  substitute 
  for 
  the 
  expression 
  

   "planes 
  of 
  foliation," 
  that 
  of 
  planes 
  having 
  the 
  mean 
  or 
  the 
  

   prevailing, 
  direction 
  of 
  the 
  foliation 
  ; 
  for 
  these 
  would 
  be 
  the 
  

   planes 
  of 
  easiest 
  cleavage 
  in 
  schists 
  of 
  great 
  thickness. 
  

  

  Again, 
  as 
  another 
  modification 
  in 
  the 
  statement 
  of 
  the 
  hy- 
  

   pothesis, 
  it 
  appears 
  necessary 
  to 
  make 
  the 
  chief 
  foliation- 
  

   planes 
  not 
  those 
  of 
  the 
  rocks 
  constituting 
  the 
  upper 
  one, 
  two 
  

  

  * 
  This 
  Journal, 
  xxxii, 
  349, 
  1886. 
  See 
  also 
  7th 
  Annual 
  Report 
  of 
  the 
  Director 
  

   of 
  the 
  U. 
  S. 
  Geological 
  Survey. 
  

  

  