﻿ACADEMY 
  OF 
  SCIENCES. 
  391 
  

  

  water 
  surrounding 
  them, 
  there 
  was 
  abundant 
  rainfall 
  and 
  luxuriant 
  vegetation, 
  

   suitable 
  for 
  the 
  animals 
  mentioned. 
  

  

  It 
  is 
  not 
  unlikely 
  that 
  some 
  of 
  these 
  animals 
  may 
  have 
  existed 
  before 
  and 
  

   after 
  the 
  pliocene 
  epoch 
  as 
  well 
  as 
  in 
  it, 
  but 
  the 
  explorations 
  are 
  still 
  insufiBcient 
  

   to 
  decide 
  this. 
  

  

  VOLCANIC 
  ERA. 
  

  

  The 
  termination 
  of 
  this 
  tropical 
  epoch 
  in 
  California 
  was 
  marked 
  (as 
  de- 
  

   scribed 
  first 
  by 
  Prof. 
  Whitney) 
  by 
  enormous 
  volcanic 
  outbursts, 
  which 
  poured 
  

   out 
  great 
  streams 
  of 
  lava 
  on 
  the 
  slope 
  of 
  the 
  Sierra 
  Nevada, 
  covering 
  entirely 
  

   large 
  tracts 
  toward 
  the 
  north. 
  At 
  the 
  same 
  time 
  the 
  whole 
  country 
  was 
  ap- 
  

   parently 
  raised 
  by 
  the 
  elevation 
  of 
  new 
  mountain 
  ranges 
  and 
  increase 
  of 
  old 
  

   ones, 
  causing 
  the 
  lakes 
  to 
  be 
  drained, 
  and 
  their 
  beds 
  filled 
  by 
  washings 
  from 
  

   the 
  hills, 
  mixed 
  with 
  volcanic 
  materials. 
  This 
  great 
  convulsion, 
  no 
  doubt, 
  ex- 
  

   terminated 
  most 
  of 
  the 
  tropical 
  flora 
  and 
  fauna 
  of 
  California, 
  although 
  some 
  

   of 
  its 
  representatives 
  might 
  have 
  existed 
  later 
  in 
  neighboring 
  regions, 
  and 
  their 
  

   descendants 
  may 
  still 
  be 
  found 
  in 
  tropical 
  America. 
  That 
  all 
  are 
  not 
  extinct, 
  

   is 
  probable 
  from 
  the 
  analogy 
  of 
  tertiary 
  species 
  elsewhere, 
  and 
  from 
  the 
  fact 
  

   that 
  most 
  of 
  the 
  marine 
  and 
  fresh-water 
  shells 
  of 
  the 
  strata 
  deposited 
  at 
  that 
  

   time 
  are 
  still 
  living 
  ; 
  some, 
  however, 
  only 
  south 
  of 
  California. 
  

  

  Many 
  extinct 
  land 
  animals 
  have 
  been 
  found 
  to 
  have 
  lived 
  in 
  Europe 
  since 
  

   the 
  appearance 
  of 
  man 
  on 
  the 
  earth, 
  and 
  there 
  is 
  strong 
  evidence 
  in 
  the 
  " 
  Cala- 
  

   veras 
  skull," 
  and 
  others, 
  that 
  the 
  same 
  fact 
  is 
  true 
  of 
  California. 
  

  

  It 
  does 
  not, 
  however, 
  necessarily 
  prove 
  that 
  man 
  existed 
  in 
  the 
  pliocene 
  

   epoch, 
  as 
  his 
  remains 
  may 
  have 
  been 
  buried 
  under 
  volcanic 
  outflows 
  of 
  later 
  

   date, 
  together 
  with 
  postpliocene 
  animals, 
  or 
  even 
  bones 
  of 
  pliocene 
  species 
  

   mixed 
  with 
  them 
  by 
  aid 
  of 
  volcanic 
  convulsions. 
  

  

  POSTPLIOCENE 
  EPOCH. 
  

  

  The 
  immense 
  period 
  of 
  time 
  that 
  has 
  elapsed 
  since 
  the 
  pliocene 
  epoch 
  is 
  

   shown 
  by 
  the 
  vast 
  accumulations 
  of 
  volcanic 
  materials 
  poured 
  out 
  by 
  Mt. 
  Ves- 
  

   uvius 
  on 
  top 
  of 
  marine 
  strata 
  of 
  shells, 
  of 
  which 
  every 
  one 
  of 
  the 
  species 
  is 
  

   said 
  to 
  be 
  living 
  in 
  the 
  Mediterranean, 
  and 
  therefore 
  of 
  late 
  postpliocene 
  date. 
  

   Yet 
  history 
  and 
  the 
  evidence 
  of 
  human 
  remains 
  go 
  back 
  through 
  only 
  a 
  thin 
  

   portion 
  of 
  these 
  volcanic 
  strata 
  ! 
  California, 
  before 
  the 
  end 
  of 
  the 
  pliocene, 
  

   was 
  certainly 
  badly 
  suited 
  for 
  the 
  existence 
  of 
  man. 
  The 
  deposits 
  formed 
  dur- 
  

   ing 
  the 
  convulsive 
  era, 
  to 
  the 
  thickness 
  of 
  hundreds 
  of 
  feet, 
  are 
  themselves 
  

   almost 
  destitute 
  of 
  all 
  fossils, 
  although 
  burying 
  such 
  a 
  rich 
  collection. 
  

  

  While 
  this 
  was 
  going 
  on 
  in 
  California, 
  there 
  was 
  probably 
  a 
  great 
  geological 
  

   change 
  taking 
  place 
  in 
  other 
  parts 
  of 
  the 
  world, 
  followed 
  by 
  the 
  glacial 
  era. 
  

   In 
  this, 
  the 
  northern 
  hemisphere, 
  down 
  to 
  about 
  lat. 
  41°, 
  was 
  mostly 
  covered 
  by 
  

   ice, 
  and 
  the 
  great 
  deposit 
  called 
  the 
  " 
  Drift" 
  formed 
  in 
  Europe 
  and 
  the 
  Eastern 
  

   States. 
  

  

  The 
  Geological 
  Survey 
  proved 
  conclusively 
  that 
  this 
  deposit 
  of 
  erratic 
  

   boulders 
  did 
  not 
  reach 
  over 
  California, 
  and 
  it 
  is 
  doubtful 
  if 
  even 
  as 
  far 
  south 
  as 
  

   Vancouver 
  Island. 
  Still, 
  the 
  influence 
  of 
  the 
  frozen 
  period 
  was 
  no 
  doubt 
  exerted 
  

  

  