﻿242 
  J. 
  Barrell 
  — 
  The 
  Piedmont 
  Terraces 
  

  

  After 
  the 
  maps 
  have 
  been 
  treated 
  in 
  this 
  manner, 
  care 
  

   being 
  taken 
  that 
  each 
  elevation 
  is 
  represented 
  by 
  the 
  

   same 
  color 
  on 
  different 
  sheets, 
  the 
  eye 
  at 
  a 
  glance 
  can 
  

   note 
  the 
  general 
  accordance 
  or 
  discordance 
  of 
  smnmit 
  

   elevations 
  and 
  can 
  more 
  easily 
  pick 
  ont 
  significant 
  

   details. 
  

  

  Method 
  of 
  projected 
  profiles. 
  — 
  An 
  ancient 
  peneplane 
  

   may 
  have 
  been 
  uplifted 
  so 
  long 
  ago 
  and 
  become 
  so 
  thor- 
  

   oughly 
  dissected 
  that 
  only 
  far-scattered 
  remnants 
  re- 
  

   main. 
  Even 
  the 
  remnants 
  will 
  have 
  been 
  cut 
  down 
  to 
  

   some 
  extent 
  below 
  the 
  original 
  surface. 
  From 
  the 
  val- 
  

   leys 
  below 
  no 
  suggestion 
  of 
  the 
  former 
  plane 
  is 
  seen, 
  but 
  

   from 
  a 
  few 
  favorable 
  positions 
  slightly 
  above 
  the 
  ancient 
  

   surface 
  the 
  eye, 
  by 
  projecting 
  the 
  remnants 
  into 
  one 
  

   view, 
  may 
  be 
  able 
  to 
  perceive 
  the 
  original 
  level 
  character. 
  

  

  The 
  range 
  of 
  vision, 
  however, 
  is 
  limited 
  ; 
  photographs 
  

   fail 
  to 
  bring 
  out 
  faint 
  details 
  of 
  distant 
  landscapes: 
  

   neither 
  eye 
  nor 
  camera 
  can 
  record 
  the 
  exact 
  levels 
  or 
  

   elevations 
  or 
  angular 
  slope 
  of 
  the 
  line 
  of 
  sight. 
  Some 
  

   method, 
  therefore, 
  is 
  needed 
  for 
  this 
  study 
  which 
  shall 
  be 
  

   founded 
  on 
  topographic 
  maps 
  and 
  which 
  shall 
  be 
  in 
  the 
  

   nature 
  of 
  a 
  vertical 
  profile, 
  yet 
  project 
  from 
  any 
  desired 
  

   direction 
  the 
  scattered 
  remnants 
  into 
  one 
  section. 
  A 
  

   belt 
  of 
  country 
  three, 
  ten, 
  or 
  twenty 
  miles 
  wide 
  may 
  be 
  

   needed, 
  depending 
  on 
  the 
  distance 
  between 
  remnants, 
  to 
  

   give 
  the 
  best 
  results. 
  The 
  projection 
  of 
  such 
  a 
  belt 
  of 
  

   country 
  upon 
  one 
  plane 
  gives 
  what 
  the 
  writer 
  has 
  called 
  

   a 
  ' 
  ' 
  projected 
  profile. 
  - 
  ' 
  

  

  In 
  constructing 
  a 
  projected 
  profile 
  the 
  horizontal 
  scale 
  

   must 
  be 
  large 
  enough 
  to 
  bring 
  out 
  essential 
  details, 
  and 
  

   generally 
  the 
  vertical 
  scale 
  must 
  be 
  exaggerated. 
  What- 
  

   ever 
  vertical 
  scale 
  is 
  adopted 
  it 
  should 
  be 
  used 
  for 
  all 
  the 
  

   profiles 
  so 
  that 
  they 
  may 
  be 
  directly 
  comparable. 
  The 
  

   width 
  of 
  the 
  belt 
  of 
  country 
  to 
  be 
  projected 
  depends 
  upon 
  

   the 
  degree 
  of 
  dissection 
  and 
  should 
  be 
  great 
  enough 
  to 
  

   give, 
  if 
  possible, 
  a 
  well 
  integrated 
  sky-line, 
  especially 
  

   when 
  the 
  problem, 
  as 
  in 
  the 
  present 
  instance, 
  deals 
  with 
  

   thoroughly 
  eroded 
  surfaces. 
  The 
  direction 
  of 
  view 
  must 
  

   be 
  chosen 
  so 
  as 
  to 
  bring 
  out 
  to 
  best 
  advantage 
  the 
  fea- 
  

   tures 
  sought. 
  It 
  is 
  not 
  always 
  possible 
  beforehand 
  to 
  

   determine 
  the 
  best 
  direction 
  of 
  view 
  from 
  the 
  topo- 
  

   graphic 
  maps 
  so 
  that 
  it 
  may 
  be 
  necessary, 
  and 
  in 
  any 
  case 
  

   it 
  is 
  generally 
  advisable, 
  to 
  make 
  several 
  projected 
  pro- 
  

   files 
  of 
  a 
  region 
  in 
  order 
  to 
  determine 
  which 
  direction 
  is 
  

   the 
  best. 
  

  

  