﻿ACADEMY 
  OF 
  SCIENCES. 
  217 
  

  

  The 
  evidence 
  of 
  this 
  is 
  sef^n 
  in 
  the 
  granite 
  and 
  slate 
  peaks, 
  wliich 
  still 
  rise 
  above 
  

   the 
  lava 
  tlood, 
  along 
  the 
  skirts 
  or 
  thinner 
  portions 
  of 
  the 
  lava. 
  This 
  underlying 
  

   portion, 
  therefore, 
  is 
  of 
  the 
  same 
  age 
  as 
  the 
  Sierras 
  ; 
  while 
  the 
  great 
  bulk, 
  i. 
  e., 
  the 
  

   lava 
  portion, 
  is 
  probably 
  of 
  the 
  same 
  age 
  as 
  the 
  Coast 
  range. 
  

  

  IV. 
  — 
  Theory 
  of 
  tue 
  Ejection 
  of 
  the 
  Lava 
  Flood, 
  and 
  of 
  the 
  Formation 
  

   OF 
  THE 
  Cascade 
  Mountains. 
  

  

  Scattered 
  over 
  the 
  surface 
  of 
  the 
  Cascade 
  lava-flood 
  there 
  are 
  ten 
  to 
  twelve 
  

   snow-clad 
  volcanic 
  peaks, 
  and 
  probably 
  many 
  other 
  smaller 
  cones. 
  It 
  is 
  simply 
  

   incredible 
  that 
  this 
  immense 
  mass 
  of 
  lava 
  has 
  issued 
  from 
  these 
  craters 
  — 
  that 
  the 
  

   force 
  of 
  ejection 
  has 
  been 
  only 
  steam 
  generated 
  by 
  the 
  contact 
  of 
  percolating 
  

   meteoric 
  waters 
  with 
  incandescent 
  fluid 
  subterranean 
  masses. 
  Tiie 
  ejection 
  of 
  

   the 
  lava-flood 
  cannot 
  be 
  accounted 
  for 
  except 
  by 
  more 
  general 
  causes, 
  afltjcting 
  

   the 
  whole 
  earth 
  — 
  except 
  by 
  those 
  great 
  agencies 
  by 
  which 
  mountain 
  chains 
  

   themselves 
  are 
  formed. 
  It 
  has 
  been 
  squeezed 
  out 
  through 
  fissures 
  by 
  powerful 
  

   lateral 
  pressure 
  produced 
  by 
  the 
  internal 
  contraction 
  of 
  the 
  whole 
  earth, 
  as 
  

   already 
  described 
  in 
  a 
  previous 
  article.* 
  

  

  But 
  there 
  seems 
  to 
  be 
  an 
  inverse 
  relation 
  (recently 
  pointed 
  out 
  by 
  Danaf) 
  be- 
  

   tween 
  the 
  amount 
  of 
  lateral 
  mashing 
  and 
  folding 
  of 
  strata 
  in 
  mountains 
  and 
  the 
  

   amount 
  of 
  fissure 
  eruptions. 
  I 
  explain 
  this 
  as 
  follows: 
  Mountain 
  ranges 
  are 
  

   formed 
  by 
  lateral 
  crushmg 
  together 
  and 
  vertical 
  upswelling 
  of 
  lines 
  of 
  thick 
  

   sediments 
  ; 
  but 
  the 
  ranges 
  thus 
  formed 
  became 
  afterwards 
  subject 
  to 
  successive 
  

   elevation 
  by 
  the 
  action 
  of 
  the 
  same 
  force 
  which 
  first 
  formed 
  them. 
  But 
  there 
  is 
  

   this 
  difference 
  between 
  the 
  first 
  formation 
  and 
  the 
  subsequent 
  increase 
  : 
  The 
  

   yielding 
  of 
  the 
  softer 
  sedimentu 
  is 
  quite 
  gradual 
  and 
  with 
  little 
  resistance, 
  and 
  

   therefore 
  with 
  little 
  heat 
  by 
  transformation 
  of 
  mechanical 
  energy 
  (according 
  to 
  

   Mallet's 
  pregnant 
  idea), 
  producing 
  only 
  metamorp/iism, 
  but 
  not 
  fusion 
  of 
  the 
  

   strata 
  ; 
  while 
  in 
  the 
  subsequent 
  increase 
  the 
  yielding 
  of 
  the 
  already 
  hardened 
  

   land 
  surface 
  is 
  with 
  muck 
  resi'^tance, 
  and 
  therefore 
  with 
  much 
  heat, 
  even 
  to 
  the 
  

   fusion 
  of 
  strata, 
  and 
  also 
  paroxysmal 
  with 
  formation 
  of 
  great 
  fissures, 
  and 
  the 
  

   out-=queezing 
  of 
  the 
  fused 
  matter 
  through 
  the 
  fissures 
  as 
  great 
  sheets 
  of 
  lava. 
  

   In 
  the 
  first 
  process 
  there 
  is 
  upswelling 
  or 
  uplifting 
  of 
  the 
  stratified 
  surface 
  ; 
  in 
  

   the 
  second, 
  an 
  ujobuilding 
  on 
  the 
  stratified 
  surface 
  by 
  the 
  out-squeezing 
  of 
  liquid. 
  

   In 
  both 
  cases 
  increase 
  of 
  height 
  is 
  the 
  same, 
  being 
  measured 
  by 
  the 
  amount 
  of 
  

   lateral 
  crushing, 
  

  

  Thus, 
  to 
  give 
  examples 
  : 
  The 
  Apalachian 
  was 
  formed 
  by 
  the 
  first 
  process 
  — 
  

   i. 
  e., 
  by 
  crushing 
  together 
  horizontally 
  and 
  upswelling 
  vertically 
  of 
  thick 
  sedi- 
  

   ments, 
  at 
  the 
  end 
  of 
  the 
  Coal 
  period 
  ; 
  its 
  subsequent 
  increase 
  at 
  the 
  end 
  of 
  the 
  

   Jurassic 
  was 
  with 
  great 
  fissure 
  eruptions. 
  The 
  Sierras 
  were 
  formed 
  by 
  the 
  first 
  

   process, 
  at 
  the 
  end 
  of 
  the 
  Jurassic. 
  A 
  second 
  elevation, 
  with 
  great 
  fissure 
  

   eruptions, 
  took 
  place 
  at 
  the 
  end 
  of 
  the 
  Tertiary. 
  The 
  Coast 
  chain 
  was 
  formed 
  

   by 
  the 
  first 
  method, 
  at 
  the 
  end 
  of 
  the 
  Miocene 
  ; 
  while 
  its 
  great 
  fissure 
  ejections 
  

  

  * 
  Am. 
  Journal 
  of 
  Science, 
  Vol. 
  IV., 
  p. 
  470. 
  t 
  Am. 
  Journal 
  of 
  Science, 
  Vol. 
  VI. 
  

  

  