Yol.  49.]  AHNIVEBSAEY  ADDEESS  OE  THE  PEESEDEXT.  IO3 
sandstones,  and  clays,  which  have  been  thrown  into  a  succession  of 
folds  and  flexures.  From  comparison  with  rocks  in  Trinidad,  this 
series  is  thought  to  be  of  Eocene  age,  and  must  have  been  laid 
down  when  there  was  a  large  land-area  in  the  vicinity.  The 
Oceanic  deposits,  which  rest  unconformably  on  this  series,  consist 
chiefly  of  fine  white  earths,  much  resembling  soft  chalk  in  general 
appearance,  together  with  subordinate  beds  of  pink  and  yellow  clay, 
and  occasional  layers  of  grey  pumiceous  sand  or  silt.  The  raised 
reefs  or  coral-rocks  which  cover  six-sevenths  of  the  surface  of 
Barbados  constitute  the  third  formation.  A  section  across  the 
island  from  east  to  west  .serves  to  show  the  mutual  relations  of 
these  three  formations,  and  exhibits  faulting  to  the  extent  of  a  few 
hundred  feet,  while  the  coral-rock  is  sometimes  seen  to  rest  directly 
on  the  fundamental  series. 
The  area  and  volume  of  the  Oceanic  Series  does  not  appear  to  be 
large ;  the  most  complete  succession  yields  an  estimated  thickness  of 
a  little  over  300  feet,  which  is  made  up  as  follows  : — Besting  uncon¬ 
formably  on  the  fundamental  rocks  are  calcareous  earths,  gradually 
becoming  more  siliceous,  and  succeeded  by  a  great  thickness  of  pure 
siliceous  Badiolarian  earths,  which  again  become  more  calcareous, 
and  are  topped  by  a  moderate  thickness  of  chalky  earths  and  marls. 
All  these  are,  in  the  main,  organic  deposits,  but  above  them  come 
very  fine-grained  argillaceous  deposits,  and  above  this,  in  one  place, 
some  25  feet  of  grey  volcanic  mudstones,  with  a  few  Badiolaria.  but 
no  calcareous  matter.  We  perceive,  then,  that  the  first  phase  was 
one  of  calcareous  deposits  containing  from  60  to  80  per  cent,  of 
carbonate  of  lime,  with  many  Globigerince  and  other  oceanic  Fora- 
minifera.  Presently  siliceous  organisms  are  found  in  increasing 
numbers,  and  at  length  we  arrive  at  the  central  part  of  the  series, 
which  is  essentially  siliceous,  some  beds  containing  77  per  cent,  of 
organic  silica,  with  less  than  *5  per  cent,  of  calcareous  matter, 
made  up  principally  of  Badiolaria,  Diatoms,  Sponge-spicules,  and 
occasional!}  associated  with  layers  of  pumiceous  sand.  Higher  up 
calcareous  organisms  again  make  their  appearance,  and  the  sequence 
of  organic  rocks  closes  with  a  second  zone  of  calcareous  material, 
the  quantity  of  carbonate  of  lime  varying  from  44  to  80  per  cent. 
Above  the  last  beds  there  is  a  rapid  change  into  fine-grained 
argillaceous  earths. 
When  we  come  to  compare  the  Barbados  rocks,  as  above  detailed, 
with  modern  Oceanic  deposits  we  can  hardly  fail  to  recognize,  more 
or  less  completely,  the  Globigerina- ooze,  the  Badiolarian  ooze,  and 
