﻿THE 
  EVIDENCE 
  OE 
  FORMER 
  GLACIAL 
  PERIODS. 
  223 
  

  

  reached 
  the 
  sea, 
  we 
  could 
  not 
  possibly 
  possess 
  even 
  this 
  evidence. 
  

   This 
  sort 
  of 
  evidence, 
  when 
  found 
  in 
  low 
  latitudes, 
  ought 
  to 
  be 
  

   received 
  as 
  evidence 
  of 
  the 
  existence 
  of 
  former 
  glacial 
  epochs, 
  and, 
  

   no 
  doubt, 
  would 
  have 
  been 
  so 
  received 
  had 
  it 
  not 
  been 
  for 
  the 
  

   erroneous 
  idea 
  that, 
  if 
  these 
  blocks 
  had 
  been 
  transported 
  by 
  ice, 
  

   there 
  ought 
  in 
  addition 
  to 
  have 
  been 
  found 
  striated 
  stones, 
  Boulder- 
  

   clay, 
  and 
  other 
  indications 
  of 
  the 
  agency 
  of 
  land-ice. 
  

  

  It 
  is, 
  of 
  course, 
  by 
  no 
  means 
  the 
  case 
  that 
  all 
  erratics 
  are 
  trans- 
  

   ported 
  by 
  masses 
  of 
  ice 
  broken 
  from 
  the 
  terminal 
  front 
  of 
  glaciers. 
  

   The 
  " 
  ice-foot 
  " 
  formed 
  by 
  the 
  freezing 
  of 
  the 
  sea 
  along 
  the 
  coasts 
  

   of 
  the 
  higher 
  latitudes 
  carries 
  seawards 
  quantities 
  of 
  blocks 
  and 
  

   debris. 
  Again, 
  stones 
  and 
  boulders 
  are 
  frequently 
  frozen 
  into 
  river- 
  

   ice, 
  and 
  when 
  the 
  ice 
  breaks 
  up 
  in 
  spring 
  are 
  swept 
  out 
  to 
  sea, 
  and 
  

   may 
  be 
  carried 
  some 
  little 
  distance 
  before 
  they 
  are 
  dropped. 
  But 
  

   both 
  these 
  cases 
  can 
  occur 
  only 
  in 
  regions 
  where 
  the 
  winters 
  are 
  

   excessive 
  ; 
  nor 
  is 
  it 
  at 
  all 
  likely 
  that 
  such 
  ice-rafts 
  will 
  succeed 
  in 
  

   making 
  a 
  long 
  voyage. 
  If, 
  therefore, 
  the 
  erratics 
  occasionally 
  met 
  

   with 
  in 
  certain 
  old 
  geological 
  formations 
  in 
  low 
  latitudes 
  were 
  really 
  

   transported 
  from 
  the 
  land 
  by 
  an 
  ice-foot 
  or 
  a 
  raft 
  of 
  river-ice, 
  we 
  

   should 
  be 
  forced 
  to 
  conclude 
  that 
  very 
  severe 
  climatic 
  conditions 
  

   must 
  have 
  obtained 
  in 
  such 
  latitudes 
  at 
  the 
  time 
  the 
  erratics 
  were 
  

   dispersed. 
  

  

  Why 
  we 
  now 
  have, 
  comparatively 
  speaking, 
  so 
  little 
  direct 
  

   evidence 
  of 
  the 
  existence 
  of 
  former 
  glacial 
  periods 
  will 
  be 
  more 
  

   forcibly 
  impressed 
  upon 
  the 
  mind 
  if 
  we 
  reflect 
  how 
  difficult 
  it 
  

   would 
  be 
  in 
  a 
  million 
  or 
  so 
  years 
  hence 
  to 
  find 
  any 
  trace 
  of 
  what 
  

   we 
  now 
  call 
  the 
  glacial 
  epoch. 
  The 
  striated 
  stones 
  would 
  by 
  that 
  

   time 
  be 
  all, 
  or 
  nearly 
  all, 
  disintegrated, 
  and 
  the 
  till 
  washed 
  away 
  

   and 
  deposited 
  in 
  the 
  bottom 
  of 
  the 
  sea 
  as 
  stratified 
  sands 
  and 
  clays. 
  

   And 
  when 
  these 
  became 
  consolidated 
  into 
  rock 
  and 
  were 
  raised 
  into 
  

   dry 
  land, 
  the 
  only 
  evidence 
  that 
  we 
  should 
  probably 
  then 
  have 
  that 
  

   there 
  ever 
  had 
  been 
  a 
  glacial 
  epoch 
  would 
  be 
  the 
  presence 
  of 
  an 
  

   occasional 
  large 
  block 
  of 
  the 
  older 
  rocks 
  found 
  imbedded 
  in 
  the 
  

   upraised 
  formation. 
  We 
  could 
  only 
  infer 
  that 
  there 
  had 
  been 
  ice 
  

   at 
  work 
  from 
  the 
  fact 
  that 
  by 
  no 
  other 
  known 
  agency 
  could 
  we 
  

   conceive 
  such 
  a 
  block 
  to 
  have 
  been 
  transported 
  and 
  dropped 
  in 
  a 
  

   still 
  sea. 
  

  

  Pew 
  geologists 
  probably 
  believe 
  that 
  during 
  the 
  Middle 
  Eocene 
  

   and 
  the 
  Upper 
  Miocene 
  periods 
  our 
  country 
  passed 
  through 
  a 
  con- 
  

   dition 
  of 
  glaciation 
  as 
  severe 
  as 
  it 
  has 
  done 
  during 
  the 
  Post-pliocene 
  

   period 
  ; 
  yet 
  when 
  we 
  examine 
  the 
  subject 
  carefully, 
  we 
  find 
  that 
  

   there 
  is 
  actually 
  no 
  just 
  ground 
  to 
  conclude 
  that 
  it 
  did 
  not. 
  Por, 
  

   in 
  all 
  probability, 
  throughout 
  the 
  strata 
  to 
  be 
  eventually 
  formed 
  

   out 
  of 
  the 
  destruction 
  of 
  the 
  now 
  existing 
  land-surfaces, 
  evidence 
  of 
  

   ice-action 
  will 
  be 
  as 
  scarce 
  as 
  in 
  Eocene 
  or 
  Miocene 
  strata. 
  

  

  Did 
  the 
  stratified 
  rocks 
  forming 
  the 
  earth's 
  crust 
  consist 
  of 
  a 
  

   series 
  of 
  old 
  land-surfaces, 
  instead 
  (as 
  they 
  actually 
  do) 
  of 
  a 
  series 
  

   of 
  old 
  sea-bottoms, 
  then 
  traces 
  of 
  many 
  glacial 
  periods 
  might 
  pro- 
  

   bably 
  be 
  detected. 
  Nearly 
  all 
  the 
  evidence 
  which 
  we 
  have 
  regarding 
  

   the 
  glacial 
  epoch 
  has 
  been 
  derived 
  from 
  what 
  we 
  find 
  on 
  the 
  now 
  

  

  Q.J.G.S. 
  No. 
  178. 
  s 
  

  

  