﻿G. 
  H. 
  Stone 
  — 
  Glaciation 
  of 
  Central 
  Idaho. 
  11 
  

  

  formation 
  of 
  Lindgren's 
  map 
  of 
  Boise 
  Basin 
  is, 
  at 
  Placerville 
  

   at 
  least, 
  of 
  glacial 
  age 
  and 
  glacial 
  origin. 
  

  

  A 
  short 
  distance 
  south 
  of 
  Elk 
  City 
  is 
  a 
  series 
  of 
  glacial 
  

   gravels 
  deserving 
  special 
  study. 
  A 
  gravel 
  plain 
  one-eighth 
  of 
  

   a 
  mile 
  to 
  about 
  a 
  fourth 
  of 
  a 
  mile 
  in 
  breadth, 
  and 
  in 
  places 
  

   eighty 
  feet 
  deep, 
  leaves 
  the 
  valley 
  of 
  Red 
  Horse 
  river, 
  and 
  

   extends 
  seven 
  miles 
  westward, 
  first 
  going 
  obliquely 
  over 
  hills 
  

   more 
  than 
  100 
  feet 
  high 
  ; 
  then 
  for 
  two 
  miles 
  is 
  on 
  the 
  top 
  of 
  

   the 
  hills 
  immediately 
  adjoining 
  the 
  American 
  river 
  on 
  the 
  

   south; 
  then 
  crosses 
  that 
  stream 
  obliquely, 
  ascends 
  a 
  hill; 
  then 
  

   crosses 
  the 
  valley 
  of 
  Elk 
  Creek 
  nearly 
  at 
  right 
  angles 
  and 
  

   ascends 
  another 
  hill 
  to 
  Buffalo 
  Hill 
  placer. 
  The 
  American 
  

   Hill 
  placer 
  is 
  part 
  of 
  this 
  gravel 
  system. 
  I 
  did 
  not 
  follow 
  the 
  

   course 
  of 
  this 
  interesting 
  gravel 
  system 
  east 
  or 
  west 
  of 
  the 
  

   points 
  named, 
  but 
  it 
  probably 
  can 
  be 
  traced 
  for 
  miles 
  in 
  both 
  

   directions. 
  The 
  direction 
  of 
  transportation 
  was 
  westward. 
  

   Above 
  the 
  point 
  where 
  this 
  gravel 
  system 
  crosses 
  the 
  American 
  

   river, 
  the 
  gravel 
  of 
  that 
  stream 
  is 
  much 
  less 
  worn 
  and 
  rounded 
  

   than 
  below 
  that 
  point. 
  The 
  materials 
  of 
  this 
  gravel 
  plain 
  are 
  

   very 
  round 
  and 
  smoothed 
  gravel, 
  cobbles, 
  bowlderets 
  and 
  even 
  

   some 
  bowlders, 
  and 
  they 
  have 
  afforded 
  millions 
  in 
  gold. 
  On 
  

   the 
  hills 
  between 
  Red 
  Horse 
  and 
  American 
  rivers 
  the 
  placer 
  

   miners 
  have 
  washed 
  away 
  the 
  overlying 
  gravel. 
  The 
  rock 
  

   beneath 
  the 
  gravel 
  is 
  very 
  much 
  smoothed 
  and 
  polished, 
  

   but 
  is 
  very 
  uneven, 
  containing 
  many 
  rounded 
  depressions, 
  

   bowls 
  and 
  pot 
  holes 
  up 
  to 
  five 
  feet 
  in 
  depth. 
  Evidently 
  here 
  

   was 
  a 
  broad 
  river 
  that 
  flowed 
  up 
  and 
  over 
  hills 
  and 
  valleys. 
  

   That 
  it 
  disregarded 
  the 
  surface 
  forms 
  of 
  the 
  land 
  proves 
  that 
  

   it 
  was 
  enclosed 
  between 
  walls 
  of 
  ice. 
  The 
  stratification 
  is 
  not 
  

   arched 
  in 
  cross 
  section 
  like 
  that 
  of 
  the 
  osar 
  proper, 
  but 
  is 
  hori- 
  

   zontal, 
  like 
  the 
  deposit 
  I 
  have 
  elsewhere 
  described 
  as 
  the 
  osar 
  

   plains 
  of 
  Maine. 
  

  

  An 
  interesting 
  feature 
  of 
  this 
  gravel 
  system 
  is 
  the 
  fact 
  that 
  

   it 
  contains 
  multitudes 
  of 
  fragments 
  of 
  cedar 
  wood, 
  mostly 
  at 
  

   certain 
  horizons 
  at 
  considerable 
  height 
  above 
  the 
  bottom 
  of 
  the 
  

   gravel. 
  Some 
  of 
  these 
  pieces 
  retain 
  their 
  original 
  state 
  and 
  

   will 
  burn 
  after 
  being 
  dried 
  ; 
  others 
  have 
  been 
  changed 
  into 
  an 
  

   imperfect 
  lignite, 
  while 
  the 
  greater 
  number 
  have 
  been 
  partly 
  

   or 
  wholly 
  silicified. 
  The 
  growth 
  rings 
  prove 
  they 
  were 
  mostly 
  

   derived 
  from 
  trees 
  of 
  considerable 
  size. 
  I 
  saw 
  no 
  pieces 
  of 
  a 
  

   whole 
  trunk; 
  all 
  had 
  been 
  split 
  and 
  broken 
  across 
  into 
  pieces 
  

   of 
  all 
  sizes 
  up 
  to 
  twelve 
  inches 
  in 
  thickness 
  and 
  up 
  to 
  eight 
  

   feet 
  in 
  length. 
  All 
  the 
  pieces 
  have 
  been 
  smoothed 
  at 
  the 
  sides 
  

   and 
  well 
  rounded 
  at 
  the 
  ends 
  and 
  angles. 
  

  

  The 
  facts 
  prove 
  that 
  here 
  was 
  once 
  a 
  river 
  of 
  water 
  flowing 
  

   through 
  a 
  stagnant 
  glacier 
  that 
  had 
  become 
  covered 
  with 
  a 
  

   forest 
  growth 
  like 
  many 
  of 
  the 
  Alaskan 
  glaciers 
  to-day. 
  No 
  

  

  