﻿Report 
  of 
  the 
  State 
  Geologist. 
  461 
  

  

  To 
  the 
  west 
  and 
  southwest 
  of 
  this 
  ridge 
  the 
  eye 
  reaches 
  with 
  

   almost 
  unbroken 
  sweep 
  across 
  a 
  terrace 
  which 
  extends 
  to 
  the 
  

   line 
  of 
  the 
  Helderbergs. 
  This 
  terrace 
  is 
  not 
  now 
  easily 
  dis- 
  

   tinguishable, 
  but 
  there 
  is 
  little 
  doubt 
  that 
  when 
  the 
  receding 
  

   waters 
  left 
  it 
  it 
  was 
  nearly 
  level. 
  With 
  the 
  rising 
  of 
  the 
  land 
  

   and 
  the 
  consequent 
  recession 
  of 
  the 
  estuary 
  waters 
  a 
  new 
  era 
  

   began. 
  The 
  Hudson 
  began 
  cutting 
  its 
  present 
  channel 
  in 
  the 
  

   estuary 
  sediments. 
  The 
  meteoric 
  waters 
  falling 
  on 
  the 
  terrace 
  

   began 
  to 
  cut 
  a 
  way 
  to 
  the 
  river 
  and 
  gradually 
  the 
  courses 
  of 
  the 
  

   larger 
  streams 
  were 
  determined 
  and 
  these 
  with 
  their 
  feeders 
  

   began 
  the 
  work 
  of 
  destroying 
  what 
  the 
  estuary 
  waters 
  had 
  built 
  

   up. 
  The 
  result 
  is 
  what 
  is 
  seen 
  to-day. 
  The 
  once 
  level 
  terrace 
  is 
  

   cut 
  up 
  into 
  irregular 
  ridges 
  and 
  hummocks, 
  and 
  it 
  is 
  only 
  by 
  the 
  

   exercise 
  of 
  the 
  imagination 
  that 
  we 
  can 
  conceive 
  of 
  the 
  filling 
  up 
  

   of 
  these 
  miniature 
  valleys 
  and 
  gorges 
  to 
  their 
  former 
  level, 
  

   marked 
  only 
  by 
  the 
  broader-topped 
  and 
  higher 
  ridges 
  which 
  

   now 
  remain. 
  

  

  To 
  return 
  now, 
  for 
  a 
  moment, 
  to 
  the 
  barrier 
  of 
  Hudson 
  river 
  

   slates 
  parallel 
  to 
  the 
  Hudson 
  river 
  up 
  to 
  the 
  Mohawk 
  at 
  Cohoes, 
  

   we 
  may 
  say 
  with 
  a 
  strong 
  degree 
  of 
  probability 
  that 
  this 
  barrier 
  

   has 
  determined 
  to 
  a 
  marked 
  degree 
  the 
  course 
  of 
  the 
  principal 
  

   drainage 
  of 
  the 
  country 
  west 
  of 
  Albany. 
  From 
  this 
  fact, 
  and 
  from 
  

   the 
  facts 
  which 
  have 
  before 
  been 
  noted 
  with 
  regard 
  to 
  the 
  height 
  

   of 
  these 
  rocks 
  above 
  the 
  level 
  of 
  the 
  river, 
  we 
  may 
  safely 
  infer 
  

   that 
  the 
  delta 
  deposits 
  of 
  coarse 
  sands 
  and 
  gravels, 
  the 
  estuary 
  

   deposits 
  of 
  laminated 
  clays 
  and 
  molding 
  sands 
  rest 
  on 
  the 
  

   unevenly 
  eroded 
  surface 
  of 
  these 
  slates. 
  Later 
  on 
  some 
  useful 
  

   hints 
  may 
  be 
  drawn 
  from 
  these 
  facts. 
  At 
  present 
  we 
  shall 
  

   consider 
  the 
  nature 
  of 
  these 
  deposits 
  and 
  their 
  relations 
  to 
  each 
  

   other. 
  

  

  The 
  cross-bedded 
  sands 
  underlie 
  the 
  stratified 
  clays 
  Generally 
  

   they 
  are 
  found 
  resting 
  on 
  the 
  Hudson 
  river 
  group 
  of 
  rocks. 
  In 
  

   places, 
  however, 
  the 
  glaciated 
  rocks 
  appear 
  to 
  have 
  been 
  swept 
  

   bare 
  of 
  the 
  sands, 
  thus 
  allowing 
  the 
  clay 
  to 
  rest 
  directly 
  on 
  the 
  

   rocks. 
  As 
  a 
  rule, 
  however, 
  the 
  sands 
  will 
  be 
  found 
  underlying 
  

   the 
  stratified 
  clays 
  ; 
  the 
  clays 
  lying 
  unconf 
  ormably 
  on 
  them. 
  

   Plates 
  I 
  and 
  II 
  show 
  this 
  unconformity. 
  

  

  In 
  regard 
  to 
  the 
  depth 
  to 
  which 
  these 
  sands 
  extend 
  nothing 
  

   certain 
  is 
  known. 
  On 
  Jay 
  street, 
  in 
  Albany 
  city, 
  the 
  Amsdell 
  

  

  