Yol.  49.] 
DISAPPEARANCE  OF  LIMESTONES. 
383 
limestones  dwindled  away  or  disappeared,  and,  on  the  other  hand, 
where  the  waters  were  free  from  sediment  the  vital  agencies 
flourished  and  built  up  the  beds  of  limestone.  He  ventured  to 
suggest  to  the  Author  the  perusal  of  this  paper  before  coming  to  a 
conclusion  on  the  subject  which  he  had  treated. 
.Mr.  IYalford  held  that  field-workers  must  know  the  truth  of 
much  that  Mr.  Rutley  had  dealt  with.  Speaking  from  knowledge 
of  Jurassic  deposits,  he  believed  in  the  attenuation  of  limestones  in 
clay-beds,  and  thought  the  nodules  and  the  way  in  which  they  w7ere 
studded  writh  fossils  often  bore  such  evidence.  Outflows  of  water  fre¬ 
quently  occurred  along  limestone-lines  in  a  clay-series.  Hear  faults 
he  had  noticed  limestones  considerably  attenuated  by  such  chemical 
solution.  And  in  the  same  way  the  ferruginous  limestones  of  the 
Middle  Lias  often  lost  all  trace  of  their  fossil  contents,  and  fossiliferous 
and  barren  beds  occurred  close  together.  Calcareous  beds  could  be 
broken  up  by  both  chemical  and  mechanical  solution,  but  the  greater 
work  was  done  where  the  limestones  and  clays  were  in  contact. 
Prof.  Judd  agreed  with  the  Author  of  the  paper  that,  in  some 
cases,  limestones  may  be  removed  wholly  or  in  part  by  solution,  and 
he  referred  to  the  solution  of  the  Chalk  below  the  Thanet  Sands 
about  London  as  an  example  of  this  action.  He  was,  however, 
unable  to  follow  the  Author  in  regarding  the  action  as  producing 
very  widespread  effects ;  the  absence  of  disturbance  in  underlying 
and  overlying  strata  (analogous  to  the  ‘  creeps  ’  produced  in  the 
removal  of  coal  or  salt)  made  it  difficult  to  believe  in  such  extensive 
disappearance  of  great  thicknesses  of  limestone  as  was  suggested. 
General  McMakon  said  that  the  Kankar  Beds  of  Northern  India 
showed  that  nodules  were  not  always  an  indication  of  the  waste  of 
limestone-beds  by  aqueous  agencies.  The  plains  of  Northern  India 
were  the  creation  of  existing  rivers  in  recent  geological  times,  and 
they  consisted  of  river-alluvium  to  a  great  but  unknown  depth. 
The  lime  set  free  by  the  decomposition  of  the  finely  triturated 
minerals  in  this  alluvium  was  brought  together  by  a  process  of 
segregation  as  carbonate,  and  formed  extensive  beds  within  a  few 
feet  of  the  surface.  This  earthy  limestone  was  distinctly  nodular. 
Prof.  T.  Rupert  Jones  mentioned  that  in  Kent  the  sandy  lime¬ 
stone  known  as  4  Kentish  Rag  ’  weathered  at  the  surface  into  stony 
soil,  and  was  disintegrated  downwards  into  blocks,  larger  and  more 
closely  connected  below,  such  as  was  shown  by  one  of  Mr.  Rutley’s 
diagrams.  In  another  case,  however,  in  Somerset,  several  distinct 
parts  of  the  skeleton  of  a  Teleosaurus ,  lying  in  the  Lias  clay,  were 
seen  to  have  been  separately  taken  up  by  nodular  concretions,  not 
at  all  connected  by  limestone. 
The  Kankar,  referred  to  by  General  McMahon,  he  had  always 
understood  was  formed  as  separate  nodules  on  and  around  the  silted 
land-  and  river-shells  and  the  scattered  bones  of  drowned  animals. 
Prof.  Hughes  believed  that  the  cases  in  which  limestones  had  dis¬ 
appeared  by  subterranean  erosion  were  very  rare,  except  where 
they  were  replaced  by  silica.  He  thought  that  we  should  seek  for 
evidence  from  the  behaviour  of  the  limestones,  where  they  are  last 
