424  Geological  Society. 
"with  reference  to  sheets  of  it  that  lie  on  fairly-even  floors.  In  such 
positions  it  varies  from  2  to  12  feet  in  depth,  and  large  areas  occur 
where  it  must  have  an  average  depth  of  3  or  4  feet.  The  products 
resulting  from  artificial  solution  of  chalk  are  then  considered,  and 
a  series  of  analyses  is  given,  from  which  the  average  amount  of 
insoluble  residue  existing  in  the  four  lower  zones  of  the  Upper 
Chalk  is  deduced.  Experiments  have  been  made  by  Mr.  AVilliam 
Hill  to  determine  the  relative  weights  of  a  cubic  foot  of  Upper 
Chalk  and  a  cubic  foot  of  Clay-with-Elints,  in  order  that  allowance 
might  be  made  for  the  difference  in  calculating  the  quantity  of  clav 
which  would  be  left  by  the  solution  of  a  given  quantity  of  chalk.  The 
result  shows  that  100  cubic  feet  of  the  Micraster-coranguinitm- 
Chalk  will  produce  only  1*2  cubic  feet  of  clay,  and  the  solution  of 
the  Marsupites-  and  Micraster-coranguimtm-Zones,  to  the  extent  of 
200  feet  over  any  part  of  the  area  would  only  yield  clav 
enough  to  make  a  layer  2  feet  deep.  Lastly,  it  is  shown  that 
the  quantity  of  flints  in  the  Upper  Chalk  is  so  much  greater  than 
the  quantity  of  clay,  that  the  natural  residue  could  not  form  a 
clay-with-flints.  Thus,  solution  of  100  feet  of  Micraster-cor- 
anguinum-Chaik  would  yield  a  bed  of  flints  about  7  feet  thick, 
and  only  enough  clay  to  fill  up  the  interstices  between  the 
nodules. 
The  next  section  is  devoted  to  the  distribution  of  the  Clay-with- 
Flints,  and  its  stratigraphical  relations  to  the  Chalk  on  the  one  hand, 
and  to  the  Eocene  on  the  other.  In  dealing  with  this  part  of  the 
subject,  details  are  restricted  to  the  areas  lying  west  and  north-west 
of  the  London  Basin  and  to  the  wide  area  between  the  London  and 
Hampshire  Basins. 
Erom  these  several  lines  of  investigation  the  author  concludes  : — 
(1)  That  the  Clay-with-Elints  cannot  have  been  formed  from  mere 
solution  of  the  Upper  Chalk.  (2)  That  all  its  components,  except 
the  unbroken  and  angular  flints,  could  have  been  furnished  by  the 
Beading  Beds.  (3)  That  the  positions  occupied  by  it  are  such  that 
no  great  thickness  of  Chalk  can  have  been  destroyed  to  form  it,  the 
tracts  being  seldom  more  than  30  or  40  feet  below  the  local  plane 
of  the  Eocene  base,  or  the  presumed  level  of  that  plane. 
Finally,  an  attempt  is  made  to  explain  the  manner  in  which  the 
Clay-with-Elints  was  formed ;  and  the  theory  adopted  is  that  the 
outlying  Eocene  tracts,  which  were  in  existence  during  late  Pliocene 
time,  were  broken  up  and  spread  out  by  the  severe  climatic  conditions 
of  the  Glacial  Period.  In  post- Glacial  time  little  has  been  added, 
but  much  removed  by  erosion. 
2.  '  On  Eootprints  from  the  Permian  of  Mansfield  (Nottingham- 
shire).'    By  George  Hickling,  B.Sc. 
