106  PROCEEDINGS  OE  THE  GEOLOGICAL  SOCIETY.  [May  1 893, 
existence  of  considerable  areas  of  Eadiolarian  ooze  in  the  tropical 
portions  of  the  North  Atlantic,  but  Dr.  Murray  is  less  sanguine 
on  this  point.1  Of  course,  there  are  plenty  of  Eadiolaria  in  the 
Atlantic,  but  their  remains  do  not  collect  in  sufficient  quantities 
to  form  a  Eadiolarian  ooze,  which  according  to  Murray’s  definition 
should  contain  not  less  than  20  per  cent,  of  Eadiolaria  and  siliceous 
organisms  other  than  Diatoms.2  Such  deposits  occur  sparingly 
in  parts  of  the  Indian  Ocean  and  in  the  central  and  western 
regions  of  the  Pacific.  Dr.  Murray  goes  on  to  remark  that  even 
Eadiolaria,  like  the  calcareous  Poraminifera,  are  slowly  dissolved 
by  sea-water,  after  the  death  of  the  organisms. 
There  is  a  general  idea,  evidently  shared  by  Jukes-Browne  and 
Harrison,  that  Eadiolarian  ooze  in  existing  seas  indicates  excessive 
depths.  Murray  himself  states  that  Eadiolarian  ooze  has  a  greater 
average  depth  than  even  the  Eed  Clay.  But  it  is  evident  that  causes 
other  than  bathymetrical  influence  in  a  remarkable  manner  all 
kinds  of  oceanic  deposits.  Attention  to  the  following  4  Challenger  ’ 
soundings  will  easily  show  this  to  be  the  case.  At  station  No.  116, 
between Pernando  Noronha  and  Pernambuco,  the  surface-temperature 
being  78°  P.  and  the  depth  2275  fathoms,  the  bottom  was  found 
to  be  what  is  called  Globigerina- ooze,  containing  65  per  cent,  of 
carbonate  of  lime ;  while  at  station  No.  259,  between  Yokohama 
and  the  Sandwich  Islands,  the  surface-temperature  being  77°  P. 
and  the  depth  2225  fathoms,  the  bottom  was  found  to  consist  of 
what  is  called  Eed  Clay  with  only  a  trace  of  carbonate  of  lime. 
On  comparing  these  two  stations,  one  in  the  Atlantic  and  the  other 
in  the  Pacific,  we  perceive  that,  while  the  surface-temperatures  and 
depths  are  almost  identical,  in  the  one  case  carbonate  of  lime,  arising 
principally  from  calcareous  organisms,  amounts  to  65  per  cent,  of 
the  whole,  whereas  in  the  other  case  there  is  scarcely  a  trace  of  it. 
Again,  with  regard  to  Eadiolarian  ooze,  which  we  have  seen 
defined  as  a  Eed  Clay  with  20  per  cent,  and  upwards  of  siliceous 
organisms  other  than  Diatoms,  some  curious  facts  may  be  gathered 
from  a  careful  perusal  of  the  Synoptical  Table  in  the  ‘  Challenger 9 
Eeport.  It  so  happened  that  at  station  No.  225,  between  the 
Admiralty  Islands  and  Yokohama,  in  the  Western  Pacific,  the 
enormous  depth  of  4475  fathoms  was  reached,  the  deepest  sounding 
from  which  a  deposit  is  known  to  have  been  procured,  and  this  was 
found  to  contain  80  per  cent,  of  Eadiolaria  and  siliceous  organisms. 
Even  in  this  case  one  or  two  Globigerincs  were  observed. 
1  Op.  cit.  p.  208.  2  Ibid.  p.  203. 
