﻿AGE 
  OF 
  THE 
  EARTH 
  — 
  CHAMBERLIN 
  AND 
  OTHERS. 
  269 
  

  

  zone 
  in 
  the 
  word 
  hemera. 
  The 
  double 
  combination 
  of 
  time 
  and 
  space 
  

   makes 
  a 
  biozone. 
  The 
  time 
  unit 
  has 
  also 
  been 
  termed 
  sceculum 
  by 
  

   Jukes-Brown, 
  moment 
  and 
  phase 
  by 
  the 
  International 
  Geological 
  

   Congress. 
  In 
  the 
  recent 
  summary 
  of 
  these 
  expressions 
  and 
  their 
  in- 
  

   terpretations 
  as 
  given 
  by 
  Diener, 
  in 
  order 
  to 
  determine 
  a 
  proper 
  basis 
  

   for 
  his 
  discussion, 
  he 
  employs 
  the 
  term 
  zone 
  for 
  the 
  spatial, 
  that 
  is 
  

   horizontal 
  and 
  vertical 
  distribution 
  of 
  a 
  fauna, 
  whose 
  time 
  is 
  a 
  

   moment. 
  

  

  The 
  whole 
  interpretation 
  of 
  these 
  conceptions 
  centers 
  upon 
  the 
  

   origin 
  and 
  endurance 
  of 
  a 
  mutation, 
  which 
  in 
  the 
  proper 
  paleontologi- 
  

   cal 
  sense 
  is 
  a 
  departure 
  from 
  a 
  recognized 
  species 
  toward 
  and 
  into 
  a 
  

   unit 
  which, 
  by 
  determinate 
  action 
  of 
  the 
  genes 
  producing 
  variation, 
  

   will 
  become 
  another 
  species. 
  That 
  is 
  to 
  say, 
  the 
  mutation 
  is 
  a 
  clearly 
  

   recognizable 
  entity 
  in 
  paleontology, 
  is 
  the 
  bridge 
  crossing 
  from 
  spe- 
  

   cies 
  to 
  species, 
  the 
  connecting 
  link 
  which 
  establishes 
  the 
  continuity 
  of 
  

   the 
  chain. 
  Apart 
  from 
  considerations 
  of 
  physiology 
  only, 
  the 
  pale- 
  

   ontologist 
  sees 
  no 
  further 
  occasion 
  for 
  debating 
  the 
  existence 
  of 
  con- 
  

   necting 
  links 
  or 
  of 
  passages 
  from 
  species 
  to 
  species, 
  or 
  as 
  to 
  how 
  

   species 
  originate. 
  The 
  mutation 
  is 
  the 
  departure 
  from 
  the 
  one, 
  seek- 
  

   ing 
  adjustment 
  and 
  failing, 
  or 
  seeking 
  and 
  finding 
  it 
  in 
  what 
  must 
  be 
  

   recognized 
  from 
  accepted 
  standards 
  as 
  a 
  distinct 
  specific 
  form, 
  a 
  dif- 
  

   ferent 
  species 
  from 
  its 
  parentage. 
  But 
  when 
  it 
  comes 
  to 
  a 
  matter 
  of 
  

   determining 
  the 
  rates, 
  the 
  time 
  measure 
  of 
  these 
  changes 
  under 
  vary- 
  

   ing 
  and 
  all 
  conceivable 
  physical 
  conditions, 
  the 
  pursuit 
  seems 
  to 
  us 
  

   hopeless, 
  hopeless 
  a 
  priori, 
  hopeless 
  in 
  observation. 
  There 
  are 
  species 
  

   that 
  have 
  held 
  their 
  own 
  without 
  change 
  through 
  the 
  ages 
  — 
  " 
  im- 
  

   mortal 
  types 
  " 
  they 
  have 
  been 
  called 
  ; 
  and 
  there 
  are 
  others 
  which 
  

   have 
  yielded 
  so 
  rapidly 
  to 
  change 
  that 
  their 
  evolution 
  is 
  explosive. 
  

   The 
  same 
  facts 
  are 
  true 
  of 
  groups 
  of 
  animals; 
  and 
  for 
  the 
  entire 
  

   organic 
  world 
  there 
  have 
  been 
  earth-wide 
  periods 
  of 
  long 
  stagnation 
  

   as 
  well 
  as 
  of 
  rapid 
  intensive 
  change. 
  So 
  long 
  as 
  an 
  estimate 
  of 
  the 
  

   age 
  of 
  the 
  earth 
  rests 
  on 
  evidence 
  of 
  the 
  rate 
  of 
  change 
  or 
  adjustment 
  

   in 
  organisms 
  through 
  the 
  acquisition 
  of 
  new 
  characters, 
  we 
  may 
  as 
  

   well 
  abandon 
  the 
  attempt 
  to 
  express 
  it 
  in 
  concrete 
  terms 
  and 
  

   satisfy 
  ourselves 
  that 
  for 
  the 
  development 
  of 
  life 
  the 
  duration 
  of 
  

   that 
  fraction 
  of 
  the 
  earth's 
  history 
  is 
  beyond 
  human 
  expression. 
  

  

  THE 
  AGE 
  OF 
  THE 
  EARTH 
  FROM 
  THE 
  POINT 
  OF 
  VIEW 
  OF 
  

   ASTRONOMY. 
  (ABSTRACT.) 
  

  

  By 
  Ebnest 
  W. 
  Brown. 
  

  

  Astronomical 
  evolution 
  is 
  considered 
  under 
  three 
  heads: 
  First, 
  

   that 
  method 
  of 
  observation 
  in 
  which 
  it 
  is 
  assumed 
  that 
  all 
  stages 
  in 
  

   the 
  process 
  are 
  visible 
  in 
  the 
  sky 
  and 
  so 
  can 
  be 
  traced 
  step 
  by 
  step. 
  

  

  