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MESSRS.  P.  LAKE  AKD  T.  T.  GROOM  OK  THE 
[Aug.  1893, 
From  the  road  upwards  for  about  500  yards  nothing  is  seen  ;  hut 
just  at  the  600-foot  contour-line  there  is  on  the  right  bank  an  ex¬ 
posure  of  black  shales  containing  graptolites  of  the  gregarius- zone. 
Fig.  5. — Sketch-map  of  Nant  Llechog ,  in  the  neighbourhood 
of  the  tivo  faults. 
a  =  Bala  Beds. 
b  —  Corwen  Grit. 
c  =  Grey  Slates. 
cl  =  Black  Shales. 
e  —  Bluish  Slates. 
f  =  Black  Shales,  with  grapto¬ 
lites  of  the  gregarius- zone. 
Note. — The  dips  of  the  Bala 
Beds  in  the  south  of  the 
map  and  of  the  portion  of 
the  graptolite-shales  in  the 
north  have  been  inadver¬ 
tently  transposed.  The  for¬ 
mer  dip  S.S.E.,  the  latter 
(the  portion  at  the  northern 
end  of  the  map)  dip  3°  W. 
of  S.  The  beds  between 
the  two  faults  are  correctly 
represented. 
Scale :  1  inch  =  40  yards  (approximately). 
These  are  best  seen  close  to  the  foot  of  a  waterfall,  the  basin  of 
which  is  hollowed  out  in  these  shales.  The  face  of  the  waterfall  is 
made  of  the  Corwen  Grit  and  of  the  slates  above  it,  and  it  is  the 
face  of  a  fault  which  runs  20°  W.  of  N.  On  the  eastern  side  of 
this  fault  lie  the  black  shales,  striking  3°  S.  of  E.,  and  on  the 
western  side  is  the  grit  with  the  slates  above  it,  striking  23°  S.  of  E. 
At  the  waterfall  the  grit  and  the  succeeding  slates  dip  towards  the 
south,  i.  e.  up  the  stream,  and  accordingly,  as  we  go  up  the  stream, 
we  reach  higher  and  higher  beds.  A  short  distance  above  the  top 
of  the  waterfall  the  slates  are  succeeded  with  perfect  regularity 
by  black  shales  like  those  below  the  waterfall,  and  in  these  we 
found  a  few  graptolites.  Then  these  graptolite-shales  are  succeeded 
by  bluish  slates,  and  these  again  by  banded  black  shales  extending  up 
