Yol.  49.] 
PLATEAU-GRAVEL  SOUTH  OE  REARING. 
323 
his  own  observations  in  the  Valley  of  the  Thames,  that  the  two  kinds  of 
gravel  (the  one  mostly  a  shingly  deposit,  with  fragments  of  sarsen  and 
without  quartzites,  etc.,  and  the  other  containing  small  boulders  and 
pebbles  of  quartzite  and  other  northern  rocks)  are  found  in  separate 
deposits  on  hills  overlooking  the  Valley,  and  in  close  proximity  to 
the  implementiferous  Valley-drift,  and  sometimes  nearly  at  the  same 
levels ;  moreover,  he  had  noticed  that  large  masses  of  each  of  these 
supposed  more  ancient  deposits  had  been  carried  bodily  into  the  old 
channel  of  the  river,  the  old  bed  being  seen  in  the  stratified  gravels 
which  are  generally  found  beneath  them.  It  is  observable  that 
these  large  masses  of  material  transported  by  ice  en  bloc  from  the 
north  often  cause  cross-bedding  where  they  stranded,  as  seen  in 
numerous  sections — though  a  more  even  stratification  is  noticeable 
in  other  places  at  the  same  contour. 
All  this  rendered  it  sometimes  very  difficult  to  determine  whether 
the  origin  of  a  particular  bed  of  gravel  was  glacial  or  fluviatile,  and 
it  was  often  hard  to  show  where  the  one  deposit  ended  and  the 
other  began.  His  own  conviction  was  that  the  very  high-level 
Valley-drifts  were  to  no  small  extent  due  to  glacial  agency,  and  in 
part  also  to  fluviatile  action ;  the  two  causes  of  deposit  appear  to 
have  been  in  operation  at  the  same  time,  and  this  was  the  condition 
of  the  Thames  Valley  in  glacial  times. 
The  two  papers  read  were  of  great  interest,  and  he  hoped  that 
future  observers  wmuld  direct  their  attention  to  the  evidence  of  the 
transport  of  very  large  masses  of  material  bodily  into  the  high-level 
Valley-drift  to  which  he  had  referred. 
Prof.  J.  F.  Blake  said  that  the  Authors  had  given  them  the  data 
without  offering  a  definite  solution  of  the  problem.  He  (the 
speaker)  did  not  find  anything  in  these  data  to  modify  his  previous 
ideas  of  the  history  of  the  Thames.  The  narrow  valley  in  which 
that  river  was  shown  in  the  diagrams  to  run  indicated  rapid  erosion, 
and  consequently  later  origin  for  the  main  stream  than  for  the 
Kennet,  which  latter  was  the  original  boundary  between  the  Northern 
and  Southern  Drift.  When  the  Goring  gorge  was  opened,  and  the 
waters  of  the  Upper  Thames  were  admitted  to  the  lower  basin,  the 
course  of  the  main  stream  was  altered,  and  then  the  Northern  Drifts 
began  to  be  cut  through. 
Mr.  W.  J.  L.  Abbott  remarked,  with  reference  to  the  eastern  end 
of  the  plateau-  upon  which  he  was  now  engaged,  that  he  had  found 
red  quartzites  similar  to  those  exhibited  up  to  over  600  feet,  to¬ 
gether  with  volcanic  and  metamorphic  rocks  about  which  he  hoped 
to  speak  on  a  future  occasion.  He  also  pointed  out  the  occurrence 
of  northern  fossils  and  boulders  at  Westcombe  Park  and  elsewhere 
in  the  south.  In  the  main  there  appeared  a  great  similarity  in  the 
drift  in  the  E.  and  W.,  but  in  the  E.  it  was  decidedly  more  fer¬ 
ruginous.  With  reference  to  the  implements  shown,  he  would  have 
liked  to  see  some  better  specimens,  such  as  had  been  found  in  the 
E.,  but  those  exhibited  were  sufficient  to  demonstrate  their  existence. 
There  were  persons,  whose  number  was  rapidly  decreasing,  who  had 
as  yet  been  unable  to  accept  these  as  man’s  work  ;  but  to  his  mind 
