Yol.  49. J 
A2TNTYEESAEY  ADDEESS  OE  THE  PEESIEEXT. 
75 
Pleistocene  succession.  Indeed,  as  we  have  already  seen,  Prof. 
Prestwich  under  a  certain  contingency  threatens  to  incorporate  it 
with  his  Westleton  Beds. 
The  South  of  England. — After  we  cross  the  Thames  there  is  no 
longer  a  Boulder-clay  of  northern  origin  to  supply  a  sort  of  rough 
chronology  to  the  various  drifts  of  this  region,  which  we  speak  of 
as  not  having  been  glaciated  in  the  ordinary  sense  of  the  term. 
Hence  the  problems  connected  with  these  various  drifts,  mostly 
perhaps  of  Pleistocene  age,  but  some  possibly  yet  more  ancient, 
are  especially  difficult  of  solution. 
Here  again  we  follow  Prof.  Prestwich,  who,  in  the  third  part  of 
his  great  paper  on  the  Westleton  Beds,  discusses  the  subject  of  a 
Southern  Drift.  The  character  and  composition  of  this  Drift  have 
long  been  known  to  geologists  through  the  writings  of  Prof.  Bupert 
Jones,  and,  more  recently,  of  Dr.  Irving  and  others.  It  is  satisfac¬ 
tory  to  find  that  on  these  points  there  is  but  little  difference  of 
opinion.  The  Southern  Drift  is  said  to  differ  from  the  Westleton 
Beds  in  a  deficiency  of  pebbles  of  old-rock  origin,  while  on  the 
other  hand  it  is  characterized  by  a  large  proportion  of  chert  and 
ragstone — not  that  these  are  wanting  in  the  Westleton  shingle,  but 
they  are  in  less  abundance,  more  reduced  in  size,  and  hold  a  more 
subordinate  position.  The  materials  common  to  both,  but  present 
in  different  proportions,  are  subangular  flints  and  flint-pebbles. 
The  Southern  Drift  or  Hill-gravels  are  then  traced  from  Kent 
into  Berkshire  ;  in  the  east  they  repose  mainly  on  the  Chalk,  in  the 
west  on  the  Tertiaries.  Owing  to  the  absence  of  organic  remains 
we  are  without  a  clue  as  to  whether  their  origin  was  fluviatile  or 
marine.  Prof.  Prestwich  thinks  it  not  improbable  that  they  are 
of  subaerial  origin,  possibly  ‘  fans  ’  such  as  are  carried  down  by 
torrents.  It  is  also  possible  that  the  cone  may  have  discharged 
under  water,  thus  spreading  out  to  a  greater  extent  and  more 
uniformly,  and  with  the  rough  sort  of  bedding  this  gravel  sometimes 
shows.  Such  an  origin  implies  something  like  a  mountain-range 
in  the  direction  of  the  Weald,  the  consideration  of  which  might 
take  us  too  far  outside  the  limits  of  Pleistocene  Geology.  It  is  suffi¬ 
cient  to  say  that  the  Author  believes  the  Southern  Drift  to  be 
somewhat  older  than  the  Westleton  shingle,  but  that  the  two 
must  at  one  time  have  proceeded  synchronously.  Hence  the 
Southern  Drift  may  range  from  late  Tertiary  to  early  Pleistocene 
times.  This  'is  as  much  as  to  say  that  they  are  pre-glacial  in  a 
certain  sense.  Dr.  Irving  thinks  that  the  chief  evidence  of  glacia- 
