[Aug.  1893, 
382  ME.  F.  RUTLEY  ON  THE  DWINDLING  AND 
Fig.  /.  Diagram  to  illustrate  the  comparative  poorness  of  the  nodular  condition 
at  the  top  of  a  series  of  thick-bedded  limestones.  On  the  left,  the 
nodules  on  the  surface  have  been  derived  from  Bed  7.  On  the  right 
they  have  been  derived  from  Bed  6.  Before  Bed  5  has  passed  into 
similar  nodules,  those  derived  from  Bed  6  will  have  wholly  disap¬ 
peared.  The  signs  X  X  denote  the  centres  of  the  original  blocks 
which  supplied  the  nodules.  On  the  right  of  the  diagram,  one  bed 
(No.  7)  has  disappeared,  Bed  6  is  represented  only  by  a  few  scattered 
nodules  or  eroded  blocks,  while  Bed  5  has  dwindled  considerably  in 
thickness,  and  its  joints  have  been  widened. 
Figs,  g,  h,  i,  and  k  represent,  diagramraatically,  the  successive  stages  in  conver¬ 
sion  of  a  series  of  thin-bedded  limestones  into  the  nodular  condition. 
s'  and  s"  denote  underlying  and  overlying  shale  or  sandstone,  or 
overlying  sandstone  and  underlying  shale. 
In  fig.  g  there  are  seven  beds  of  limestone. 
In  fig.  h  two  of  the  beds  have  passed  into  nodular  bands,  two  others 
have  been  greatly  reduced  in  thickness  and  their  joints  have  been 
widened,  while  two  more  have  dwindled  to  a  slight  extent. 
In  fig.  i  only  one  bed  (No.  4)  remains,  and  that  is  greatly  reduced  ; 
the  other  beds  are  represented  only  by  nodules. 
Fig.  k  represents  the  penultimate  stage,  wherein  the  central  bed  of 
the  series  (No.  4)  is  reduced  to  a  band  ol  nodules  surrounded  by  shale 
or  sandstone.  These  nodules  are  all  that  remains  of  the  sei'ies  of  seven 
beds.  When  they  disappear,  the  bed  s"  will  rest  directly  upon  the  bed  s'. 
Discussion. 
The  President  said  that  the  paper  raised  practical  and  theoretical 
questions  of  great  importance.  He  thought  that  the  Authors 
statements  as  to  the  thicknesses  of  the  limestones  in  the  several 
formations  were  open  to  doubt.  The  thickness  depended  on  local  con¬ 
ditions.  His  own  experience  in  the  Jurassic  rocks  did  not  bear  out 
the  Author’s  views.  The  ‘  doggers  ’  were  not  due  to  the  degrada¬ 
tion  of  a  pre-existing  bed,  but  to  concretionary  action. 
Prof.  Hull  was  gratified  that  Mr.  Eutley  had  endeavoured  to 
account  for  the  formation  of  calcareous  nodules  among  beds  of 
sand  or  shale,  but  could  not  accept  his  suggestion  that  the  absence 
or  sparseness  of  limestones  among  some  of  the  older  formations  of 
the  British  Isles  was  to  be  accounted  for  on  the  grounds  suggested 
by  the  Author.  The  presence  or  absence  of  limestones  among 
inarin^  formations  was  the  result  of  the  physical  conditions  of  the 
ocean-bed  at  different  periods  ;  and,  as  such  beds  of  limestone  were 
formed  mainly  by  vital  agencies,  where  the  conditions  had  been 
unfavourable  to  the  development  of  marine  forms,  limestones  were 
absent  or  only  slightly  represented.  These  views  were  illustrated 
by  reference  to  the  distribution  of  limestones  among  the  Triassic 
strata  of  the  Eastern  Alps  and  the  Hummulitic  Limestone  of  the 
Middle  Eocene  period.  Some  years  ago  he  (Prof.  Hull)  had  read  a 
paper  before  this  Society  (Quart.  Journ.  Geol.  Soc.  vol.  xviii.  1862, 
p.  127)  showing  how  the  limestones  on  the  one  hand,  and  the 
sedimentary  strata  on  the  other,  of  British  formations  were  deve¬ 
loped  in  their  maximum  strength  from  opposite  directions  ;  the 
agencies  by  which  .they  were  respectively  developed  being  mutually 
antagonistic  (the  one  being  vital,  the  other  mechanical),  it  was 
shown  that  where  the  sediments  predominated  in  the  waters  the 
