﻿218 
  

  

  PROCEEDINGS 
  OF 
  THE 
  CALIFORNIA 
  

  

  took 
  place 
  at 
  the 
  end 
  of 
  the 
  Tertiary, 
  or 
  later. 
  So 
  also 
  with 
  the 
  Cascades. 
  

   This 
  rani^e 
  was 
  first 
  ibrmed 
  like 
  the 
  Sierras, 
  and 
  by 
  the 
  same 
  method, 
  at 
  the 
  

   end 
  of 
  the 
  Jurassic 
  ; 
  while 
  its 
  great 
  subsequent 
  increase, 
  at 
  the 
  end 
  of 
  the 
  Mio- 
  

   cene, 
  was 
  by 
  floods 
  of 
  ejected 
  matter. 
  In 
  the 
  first 
  three 
  cases 
  the 
  range 
  was 
  

   born, 
  neai'ly 
  full-grown, 
  by 
  the 
  first 
  method 
  ; 
  while 
  in 
  the 
  case 
  of 
  the 
  Cascades 
  

   the 
  great 
  bulk 
  was 
  produced 
  by 
  the 
  second 
  method. 
  

  

  The 
  main 
  point 
  of 
  this 
  theory 
  is 
  equally 
  tenable, 
  whether 
  we 
  regard 
  the 
  sub- 
  

   mountain 
  liquid 
  as 
  locally 
  formed 
  by 
  transformation 
  of 
  mechanical 
  energy 
  into 
  

   heat, 
  as 
  maintained 
  by 
  Mallet, 
  or 
  whether 
  we 
  regard 
  it 
  as 
  a 
  remnant 
  of 
  the 
  

   original 
  sub-crust 
  fire-sea 
  of 
  Dana. 
  

  

  Y. 
  — 
  Some 
  Points 
  suggested 
  by 
  Previous 
  Discussion. 
  

  

  The 
  author 
  then 
  mentioned 
  briefly 
  several 
  important 
  subjects, 
  which 
  require 
  

   additional 
  observation. 
  

  

  a. 
  The 
  successive 
  flows 
  by 
  which 
  the 
  Cascade 
  Mountains 
  are 
  built 
  up, 
  are 
  in 
  

   many 
  cases 
  easily 
  detected. 
  In 
  the 
  section 
  made 
  by 
  the 
  CohiniVjia 
  River, 
  the 
  

   lava 
  is 
  arranged 
  in 
  layers, 
  one 
  above 
  the 
  other 
  ; 
  ten 
  or 
  twelve 
  may 
  be 
  counted, 
  

   and 
  many 
  others 
  are 
  concealed 
  by 
  debris. 
  In 
  the 
  Des 
  Chutes 
  River 
  canon 
  at 
  

   least 
  thirty 
  may 
  be 
  detected, 
  and 
  doubtless 
  many 
  others 
  are 
  concealed 
  by 
  debris. 
  

   These 
  layers 
  sometimes 
  evidently 
  indicate 
  separate 
  flows 
  ; 
  sometimes 
  more 
  

   doubtfully. 
  

  

  6. 
  The 
  sections 
  made 
  by 
  the 
  Columbia 
  and 
  Des 
  Chutes 
  rivers 
  afford 
  a 
  splendid 
  

   opportunity 
  of 
  testing 
  the 
  truth 
  of 
  Richthofen's 
  view, 
  that 
  there 
  is 
  an 
  invari- 
  

   able 
  order 
  of 
  succession 
  in 
  the 
  appearance 
  at 
  the 
  surface, 
  by 
  fissure 
  eruption, 
  of 
  

   the 
  different 
  kinds 
  of 
  eruptive 
  rocks. 
  The 
  author 
  made 
  some 
  observations 
  which 
  

   seemed 
  to 
  confirm, 
  and 
  others 
  which 
  seemed 
  to 
  oppose, 
  Richthofen's 
  view. 
  He 
  

   does 
  not, 
  however, 
  consider 
  his 
  observations 
  conclusive. 
  

  

  c. 
  Formation 
  of 
  CoUimhia 
  River 
  canon. 
  The 
  lava-flood 
  was 
  formed 
  by 
  fissure 
  

   eruptions, 
  which 
  continued, 
  probably, 
  through 
  the 
  later 
  Tertiary 
  period, 
  and 
  

   then 
  continued, 
  in 
  spots, 
  by 
  crater 
  eruption 
  almost 
  till 
  now. 
  The 
  erosion 
  of 
  the 
  

   canons 
  took 
  place 
  subsequently 
  to 
  the 
  lava 
  flood. 
  The 
  Columbia 
  River 
  and 
  

   Des 
  Chutes 
  River 
  canons, 
  like 
  nearly 
  all 
  our 
  great 
  canons, 
  were 
  formed 
  since 
  

   the 
  Tertiary. 
  The 
  author 
  thinks 
  that 
  in 
  the 
  canon 
  of 
  the 
  Columbia 
  the 
  work 
  

   of 
  the 
  post-'I'ertiary 
  may 
  be 
  distinguished 
  from 
  the 
  work 
  of 
  the 
  present 
  epoch. 
  

   Fio". 
  3 
  is 
  a 
  diagramic 
  section 
  across 
  the 
  Columbia 
  River 
  caiion 
  at 
  the 
  Cascades. 
  

  

  Fig. 
  3. 
  

  

  