﻿J. 
  jS. 
  Diller 
  — 
  Crater 
  Lake, 
  Oregon. 
  167 
  

  

  observed 
  in 
  many 
  large 
  volcanoes 
  and 
  clearly 
  points 
  to 
  Crater 
  

   Lake 
  as 
  the 
  site 
  of 
  such 
  a 
  mountain. 
  

  

  The 
  rim 
  is 
  intersected 
  by 
  a 
  number 
  of 
  vertical 
  dikes, 
  some 
  

   of 
  which 
  stand 
  out 
  prominently 
  upon 
  its 
  inner 
  slope. 
  The 
  

   largest 
  of 
  these, 
  locally 
  known 
  as 
  the 
  Devil's 
  Backbone, 
  varies 
  

   from 
  five 
  to 
  twenty 
  -feet 
  in 
  thickness, 
  and 
  as 
  seen 
  in 
  the 
  plate, 
  

   cuts 
  the 
  rim 
  from 
  water 
  to 
  crest 
  one 
  and 
  a 
  half 
  miles 
  southwest 
  

   of 
  Llao 
  Rock. 
  Nearly 
  a 
  dozen 
  other 
  dikes 
  appear 
  in 
  various 
  

   parts 
  of 
  the 
  rim, 
  and 
  all 
  radiate 
  more 
  or 
  less 
  directly 
  from 
  the 
  

   lake. 
  Some 
  of 
  them 
  cut 
  through 
  the 
  older 
  lavas 
  only. 
  Others 
  

   reach 
  to 
  the 
  top 
  of 
  the 
  rim, 
  but 
  none 
  was 
  seen 
  to 
  penetrate 
  

   the 
  late 
  flows 
  of 
  rhyolite. 
  The 
  dikes 
  are 
  of 
  andesite, 
  and 
  

   their 
  radial 
  arrangement, 
  as 
  well 
  as 
  the 
  succession 
  of 
  lavas, 
  

   point 
  to 
  the 
  middle 
  portion 
  of 
  the 
  lake 
  as 
  the 
  center 
  from 
  

   which 
  they 
  emanated. 
  

  

  The 
  name 
  Crater 
  Lake 
  suggests 
  that 
  the 
  lake 
  occupies 
  a 
  

   crater, 
  and 
  it 
  would 
  naturally 
  be 
  supposed 
  that 
  the 
  crater 
  was 
  

   originally 
  as 
  large 
  as 
  the 
  rim 
  of 
  the 
  lake. 
  That 
  this 
  is 
  not 
  the 
  

   case, 
  however, 
  is 
  indicated 
  by 
  the 
  following 
  consideration. 
  

  

  No 
  lava 
  came 
  out 
  through 
  the 
  flanks 
  of 
  the 
  rim 
  excepting 
  the 
  

   basalts 
  which 
  are 
  associated 
  with 
  cinder 
  cones 
  low 
  on 
  its 
  outer 
  

   slope. 
  The 
  lava 
  streams 
  generally 
  reach 
  up 
  to 
  the 
  crest 
  and 
  

   radiate 
  from 
  the 
  rim. 
  If 
  the 
  crater 
  were 
  as 
  large 
  as 
  the 
  rim, 
  

   the 
  lavas 
  must 
  have 
  escaped 
  by 
  overflow 
  from 
  its 
  lowest 
  point, 
  

   and 
  the 
  inner 
  slope 
  of 
  the 
  rim 
  would 
  bear 
  traces 
  of 
  the 
  rise 
  

   and 
  fall 
  of 
  the 
  lava 
  within, 
  instead 
  of 
  exposing 
  sections 
  of 
  all 
  

   the 
  coulees 
  and 
  sheets 
  of 
  conglomerate 
  of 
  which 
  it 
  is 
  made 
  

   up. 
  The 
  inner 
  slope 
  of 
  the 
  rim 
  is 
  one 
  of 
  fracture 
  and 
  not 
  of 
  

   flow, 
  and 
  shows 
  that 
  the 
  lava 
  streams 
  once 
  extended 
  farther 
  

   towards 
  the 
  center 
  of 
  the 
  lake 
  than 
  now 
  and 
  were 
  more 
  elevated 
  

   in 
  that 
  direction. 
  They 
  issued 
  from 
  the 
  crater 
  or 
  sides 
  of 
  a 
  

   huge 
  volcanic 
  peak 
  which 
  once 
  stood 
  upon 
  the 
  present 
  site 
  of 
  

   the 
  lake. 
  

  

  The 
  rim 
  of 
  the 
  lake 
  has 
  been 
  extensively 
  glaciated 
  and 
  

   affords 
  ample 
  evidence 
  concerning 
  a 
  change 
  in 
  the 
  topography 
  

   of 
  the 
  region 
  since 
  the 
  glacial 
  period. 
  Moraines 
  are 
  widely 
  

   spread 
  over 
  a 
  large 
  part 
  of 
  the 
  rim, 
  and 
  extend 
  in 
  some 
  cases 
  

   far 
  beyond 
  it 
  down 
  the 
  principal 
  lines 
  of 
  drainage 
  upon 
  both 
  

   sides 
  of 
  the 
  range. 
  The 
  glacial 
  debris 
  is 
  occasionally 
  accumu- 
  

   lated 
  in 
  well-defined 
  ridges 
  transverse 
  to 
  the 
  direction 
  of 
  glacial 
  

   motion, 
  but 
  more 
  commonly 
  is 
  spread 
  over 
  the 
  region 
  in 
  an 
  

   irregular 
  veneering 
  composed 
  of 
  bowlders, 
  gravel 
  and 
  sand. 
  

   From 
  the 
  main 
  highway 
  to 
  the 
  lake 
  is 
  a 
  wagon 
  road 
  which 
  

   ascends 
  over 
  a 
  steep 
  slope 
  littered 
  with 
  many 
  bowlders 
  and 
  

   irregular 
  piles 
  of 
  glacial 
  debris. 
  On 
  the 
  east 
  of 
  the 
  road 
  

   is 
  the 
  crest 
  of 
  the 
  range. 
  Against 
  the 
  rim 
  of 
  the 
  lake 
  this 
  

   crest 
  ends 
  in 
  a 
  prominent 
  moraine 
  ridge 
  marking 
  the 
  line 
  of 
  

  

  