﻿710 
  Mutations 
  

  

  is 
  quite 
  sufficient 
  to 
  enable 
  us 
  to 
  discern 
  the 
  

   laws 
  and 
  to 
  conjecture 
  the 
  outlines 
  of 
  the 
  whole 
  

   scheme 
  of 
  evolution. 
  

  

  A 
  grave 
  objection 
  which 
  has 
  often, 
  and 
  

   from 
  the 
  very 
  outset, 
  been 
  urged 
  against 
  Dar- 
  

   win's 
  conception 
  of 
  very 
  slow 
  and 
  nearly 
  im- 
  

   perceptible 
  changes, 
  is 
  the 
  enormously 
  long 
  time 
  

   required. 
  If 
  evolution 
  does 
  not 
  proceed 
  any 
  

   faster 
  than 
  what 
  we 
  can 
  see 
  at 
  present, 
  and 
  if 
  

   the 
  process 
  must 
  be 
  assumed 
  to 
  have 
  gone 
  on 
  

   in 
  the 
  same 
  slow 
  manner 
  always, 
  thousands 
  of 
  

   millions 
  of 
  years 
  would 
  have 
  been 
  needed 
  to 
  de- 
  

   velop 
  the 
  higher 
  types 
  of 
  animals 
  and 
  plants 
  

   from 
  their 
  earliest 
  ancestors. 
  

  

  Now 
  it 
  is 
  not 
  at 
  all 
  probable 
  that 
  the 
  duration 
  

   of 
  life 
  on 
  earth 
  includes 
  such 
  an 
  incredibly 
  

   long 
  time. 
  Quite 
  on 
  the 
  contrary 
  the 
  lifetime 
  

   of 
  the 
  earth 
  seems 
  to 
  be 
  limited 
  to 
  a 
  few 
  

   millions 
  of 
  years. 
  The 
  researches 
  of 
  Lord 
  Kel- 
  

   vin 
  and 
  other 
  eminent 
  physicists 
  seem 
  to 
  leave 
  

   no 
  doubt 
  on 
  this 
  point. 
  Of 
  course 
  all 
  esti- 
  

   mates 
  of 
  this 
  kind 
  are 
  only 
  vague 
  and 
  approx- 
  

   imate, 
  but 
  for 
  our 
  present 
  purposes 
  they 
  may 
  

   be 
  considered 
  as 
  sufficiently 
  exact. 
  

  

  In 
  a 
  paper 
  published 
  in 
  1862 
  Sir 
  William 
  

   Thomson 
  (now 
  Lord 
  Kelvin) 
  first 
  endeavored 
  to 
  

   show 
  that 
  great 
  limitation 
  had 
  to 
  be 
  put 
  upon 
  

   the 
  enormous 
  demand 
  for 
  time 
  made 
  by 
  Lyell, 
  

   Darwin 
  and 
  other 
  biologists. 
  From 
  a 
  consider- 
  

  

  