448  KEV.  J.  E.  BLAKE  OK  EELSITES  AND  [Aug.  1893, 
which  the  line  from  8  to  17  forms  the  western  part.  Now  between 
the  exposures  at  2  and  8  i"  the  railway-section  there  is  a  very 
considerable  mass  of  Banded  Pale  Slate  and  other  easily  recognizable 
rocks;  if  therefore  there  is  here  such  a  continuous  synclinal,  we  ought 
to  find  the  same  series  between  19  and  25,  and  between  23  and  11 : 
but  this  is  by  no  means  the  case.  All  the  area  of  which  26  and 
27  show  good  exposures  is  a  valley  occupied  by  the  Pale  Slates ; 
but  the  line  across  from  19  to  25  is  occupied  by  rough  weathering 
crags  of  coarse  felspathic  grits  (some  of  them  with  small  white 
quartz-pebbles),  and  the  same  kind  of  rock  continues  to  the  summit 
of  Y  Bigl.  The  very  fact  of  the  highest  hill  in  the  district  fol¬ 
lowing  on  the  line  of  strike  of  a  broad  valley  seems  to  denote 
some  change  in  the  strata,  such  as  we  actually  see,  and  these 
strata  being  horizontal  and  on  the  eastern  side  certainly  con¬ 
tinuous  with  the  conglomerates,  the  whole  must  overlie  the  Pale 
Slates. 
There  are,  however,  spots  where  we  can  actually  see  this  to  be  the 
case.  Thus  at  30  we  find  the  following  section  exposed  in  a  crag 
(fig.  3).  Much  contortion  is  here  seen ;  but  there  can  be  no  question 
Pig.  3. — Y  Bigl :  Grits  overlying  Pale  Slates , 
that  the  grits,  which  are  continuous  in  the  same  form  to  the 
summit,  overlie  the  Pale  Slates.  They  show  also  obscure  signs  of 
horizontal  lamination,  and  from  the  contortions  we  learn  that  it 
would  be  very  possible  for  the  underlying  rocks  to  protrude 
occasionally  in  unexpected  spots.  Thus  at  32  a  curious  patch  of 
felsitic  ash  associated  with  banded  purple  slate  (probably  the  band 
alluded  to  by  Sir  Archibald  Geikie)  may  be  accounted  for  perhaps 
in  this  way. 
Something  very  similar  to  the  above  is  seen  at  31 ;  compare  fig.  4, 
p.  449.  Here  we  mount  over  one  boss  composed  of  Pale  Slates, 
cleaved  at  a  high  angle,  and  reach  a  higher  one  showing  easterly¬ 
dipping  beds  of  fine  irregular  grit.  Even  if  this  latter  point  were  a 
mistaken  observation,  and  the  grits  by  a  reversed  dip  were  under  the 
slates,  they  would  still  be  to  the  east  or  on  the  wrong  side ;  and  if 
