Yol.  49.]  ANNIVERSARY  ADDRESS  OF  THE  PRESIDENT.  97 
geological  time  to  years.  Such  was  conspicuously  the  case  when 
Mr.  Reade’s  paper  was  brought  before  the  Society.  Undoubtedly, 
when  the  slopes  were  steeper,  the  rate  of  denudation  and  conse¬ 
quently  of  deposition  would  be  more  rapid,  and  this  fact  is  held  by 
some  to  invalidate  any  calculations  based  on  the  present  rate  of 
deposition  of  silt. 
Misconceptions  regarding  the  Evidence  of  former  Glacial  Periods. — 
Lastly,  we  possess  in  the  paper  which  bears  the  above  title  a  legacy 
which  the  late  Dr.  Croll  may  be  almost  said  to  have  bequeathed  to 
the  Geological  Society.  His  cardinal  point  was  that  the  evidences 
of  glaciation  are  to  be  found  principally  on  land-surfaces,  and  that 
the  transformation  of  a  land-surface  into  a  sea-bottom  would 
probably  obliterate  every  trace  of  glaciation. 
He  even  went  so  far  as  to  assert  that  the  absence  of  large  erratic 
blocks  in  the  stratified  beds  may  indicate,  in  some  cases,  a  period  of 
extreme  glaciation.  The  more  complete  the  glaciation,  says  Dr. 
Croll,  the  less  probability  of  the  ice-sheet  containing  any  blocks, 
since  the  rocks  Avould  be  covered  up.  This  assertion  was  especially 
aimed  at  Rordenskj  old’s  statement  that  there  is  no  evidence  of 
glacial  conditions  in  the  strata  of  Greenland  and  Spitzbergen  down 
10  the  termination  of  the  Miocene  period,  the  absence  of  large 
boulders  being  conspicuous  in  beds  of  that  or  earlier  date.  It  suited 
Dr.  Croll  wholly  to  ignore  the  character  of  the  faunas  and  floras 
which  have  been  discovered  in  these  high  latitudes.  Moreover, 
he  seems  to  have  been  unaware  that,  by  adopting  this  line  of 
argument,  he  was  claiming  for  pre-Miocene  times  a  greater  amount 
of  glaciation  than  that  which  prevails  in  Greenland  and  Spitzbergen 
at  the  present  day.  Neither  of  these  countries  now  presents  the 
phase  which  marks  the  complete  glaciation  imagined  by  Dr.  Croll, 
since  there  is  abundance  of  morainic  matter  and  rock-detritus  at 
the  margins  of  the  inland  ice. 
The  real  state  of  the  case  seems  to  have  been  that  Dr.  Croll,  as 
an  astronomer  and  mathematician,  was  perpetually  calling  upon 
geologists  to  find  evidence  of  the  truth  of  his  favourite  hypothesis, 
viz.  the  recurrence  of  glacial  epochs.  These  latter  for  the  most 
part  have  been  wholly  unable  to  respond  to  the  call,  and,  except  in  the 
doubtful  eases  previously  mentioned,  it  can  hardly  be  said  that  there 
is  any  positive  evidence  in  support  of  Dr.  Croll’s  cardinal  point, 
although  we  cannot  help  admiring  the  dexterity  with  which  he 
contrived  to  fire  a  Parthian  shot  into  the  camp  of  the  enemy. 
