DR.  HOOKER'S  ADDRESS  TO  THE  BRITISH  ASSOCIATION.  559 
know  nothing  for  certain,  and  of  no  small  proportion  we  are  ut- 
terly ignorant. 
If,  however,  much  is  uncertain,  all  is  not  so,  and  the  science 
has  of  late  made  sure  and  steady  progress,  and  developed  really 
grand  results.  Heer's  labors  on  the  miocene  and  pliocene  floras 
especially  are  of  the  highest  value  and  interest ;  his  conclusions 
regarding  the  flower  of  the  Bovey  Tracy  coal  beds  (for  the  publi- 
cation of  which,  in  a  form  worthy  of  their  value  and  of  their 
author's  merit,  we  are  indebted  to  the  wise  liberality  of  Miss 
Burdett  Coutts)  are  founded  on  a  sufficient  number  of  absolute 
determinations  ;  and  his  more  recent  Flora  Fossilis  Arctica 
threatens  to  create  a  revolution  in  Tertiary  Geology.  In  this 
latter  work,  Prof.  Heer  shows,  on  apparently  unassailable  evi- 
dence, that  forests  of  Austrian,  American,  and  Asiatic  trees 
flourished  during  miocene  times  in  Iceland,  Arctic  Greenland, 
Spitzbergen,  and  the  Polar  American  Islands,  in  latitudes  where 
such  trees  could  not  now  exist  under  any  conceivable  conditions 
or  positions  of  land,  or  sea,  or  ice,  and  leaving  little  doubt  but 
that  an  arboreous  vegetation  once  extended  to  the  Pole  itself. 
Discoveries  such  as  these  appear  at  first  actually  to  retard  the 
progress  of  science,  by  confounding  all  previous  geological 
reasoning  as  to  the  climate  and  condition  of  the  globe  during  the 
tertiary  epoch. 
I  have  said  that  the  greatest  botanical  discoveries  made  during 
the  last  ten  years  have  been  physiological,  and  I  here  alluded 
especially  to  the  series  of  papers  on  the  "  Fertilization  of 
Plants,"  which  we  owe  to  Mr.  Darwin.  You  are  aware  that 
this  distinguished  naturalist,  after  accumulating  stores  of  facts 
in  Geology  and  Zoology  during  his  circumnavigation  of  the  globe 
with  Captain  Fitzroy,  espoused  the  doctrine  of  the  continuous 
evolution  of  life,  and  by  applying  to  it  the  principles  of  natural 
selection,  evolved  his  theory  of  the  origin  of  species.  Instead  of 
publishing  these  views  as  soon  as  conceived,  he  devoted  twenty 
more  years  to  further  observation,  study,  and  experiment,  with 
the  view  of  maturing  or  subverting  them.  Amongst  the  subjects 
requiring  elucidation  or  verification  were  many  that  appertained 
to  Botany,  but  which  had  been  overlooked  or  misunderstood  by 
botanical  writers,  and  these  he  set  himself  to  examine  vigor- 
ously. 
