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REV.  J.  F.  BLAKE  OIST  FELSITES  AND 
[Aug.  1893, 
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then  we  have  here  a  series  of  rocks  of  different  character,  nearly 
horizontal,  and  with  a  strike  at  right  angles  to  the  highly-dipping 
Purple  Slates ;  so  that  they  are  all  hut  actually  seen  to  overlie  them 
unconform  ably.  Moreover,  if  I  understand 
rightly  the  section  given  by  Mr.  Maw  (op.  cit. 
fig.  1)  of  an  adit  in  “  the  neighbouring  Glyn 
Quarries,”  it  runs  beneath  these  very  grits  and 
conglomerates,  yet  it  passes  through  200  feet 
of  Purple  Slate,  including  the  dyke  of  green¬ 
stone,  without  meeting  any  of  these  rocks  that 
are  seen  on  the  surface.  I  do  not  see,  then, 
how  the  rocks  here  described  can  possibly  lie 
naturally  below  the  Purple  Slates.  Their 
position  in  the  cutting  at  a  lower  level  and 
with  a  different  dip  is  easily  explained  by  the 
slight  fault  which  is  there  seen. 
Along  the  road  we  easily  trace  the  banded 
green  grit  l  at  5  (which  is  to  be  correlated 
in  all  probability  with  the  St.  Ann’s  Grit, 
though  each  development  has  its  own  peculi¬ 
arities),  followed  by  the  Purple  Slate  i  at  6, 
and  then,  near  the  Glyn  Peris  Hotel,  we  enter 
on  a  remarkable  group  of  rocks,  which  I  for¬ 
merly  mistook  in  part  for  the  representatives  of 
the  Phiw-wen  Grit  and  in  part  for  those  of  the 
Banded  Slates.  This  mistake  arose  from  an  in¬ 
sufficient  understanding  of  the  railway-cutting, 
which,  with  its  demonstrated  synclinal  with 
conglomerate  at  the  base,  now  proves  the  whole 
group  to  belong  to  the  overlying  series,1  and 
explains  the  curious  remark  made  to  me  by  a 
local  quarry  man,  that  he  could  not  understand 
these  rocks,  “  they  seem  to  lie  like  a  nightcap 
on  the  workable  slates.”  In  the  grounds 
between  the  Glyn  Peris  Hotel  and  the  railway 
we  find  at  7,  etc.,  the  conglomerate  and  breccia 
well  exposed  ;  but  in  parts,  as  at  8,  the 
crags  show  the  grey  slaty  grits  /  (formerly 
called  Pale  Slates).  In  places  the  bedding  is 
seen  to  be  horizontal,  but  it  gets  very  disturbed 
near  8,  just  as  we  should  expect  from  the  cutting.  My  former  attempt 
to  separate  here  the  slatier  parts  from  the  conglomerates  and  fine 
grits  led  to  a  rather  complicated  map,  which  may  now  be  simplified, 
by  uniting  them  all  as  interchangeable  portions  of  one  post-Llanberis 
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1  It  follows  that  the  words  in  Quart.  Journ.  Geol.  Soe.  vol.  xlviii.  (1892) 
p.  254,  referring  to  the  Bhiw-wen  Grit,  ‘  and  is  seen  also  to  overlie  Pale  Banded 
8 late  in  the  cliff  at  the  bend  of  the  Cwru-y-glo  road  ;  ’  and  on  p.  256,  ‘  we  find 
similar  Pale  Banded  Slates  beautifully  exposed  in  the  crag  at  the  bend  of  the  road, 
west  of  the  Glyn  Peris  Hotel.  Here  they  certainly  come  below  the  Bhiw-wen 
Grit,’  must  be  deleted. 
