But  before  the  deposition  of  the  Old  Red  and  Car-
boniferous series,  there  is  reason  to  believe  that  a  wide
and  deep  valley  already  existed  between  the  Grampian
mountains  and  the  Carrick,  Lammermuir,  and  Moorfoot
range  ;  and  in  this  hollow  the  Old  Red  Sandstone  was
deposited,  partly  derived  from  the  waste  of  the  Silurian
hills  on  the  north  and  south.  But  by-and-by,  as  depo-
sition progressed,  the  land  began  to  sink  on  the  south,
and  the  upper  strata  of  Old  Red  Sandstone  overlapped
the  lower  beds,  and  began,  as  it  were,  to  creep  south-
wards across  the  Lammermuir  Hills,  which,  sinking  still
further,  were  in  turn  invaded  by  the  lower  Coal-mea-
sures and  Carboniferous  Limestone  series.  It  appears,
therefore,  from  a  consideration  of  all  the  circumstances
connected  with  the  physical  relations  of  the  strata,  that
the  Coal-measures  once  spread  right  across  the  Lam-
mermuir range,  and  were  united  to  the  Carboniferous


296  Analysis  of  the

strata  that  now  occupy  the  north  of  England,  thus,  with
part  of  the  Old  Eed  Sandstone,  covering  great  part  of
the  Silurian  strata  of  the  south  of  Scotland.  This  un-
conformable  covering  has,  however,  in  the  course  of  re-
peated denudations,  been  removed  from  the  greater
part  of  that  high  area,  and  now  the  Carboniferous  strata
are  only  found  in  force  in  the  great  central  valley
through  which  flow  the  rivers  Forth  and  Clyde.
This  will  be  easily  understood  by  referring  to  the
section,  fig.  55,  across  the  central  valley  of  Scotland,
from  the  Grampian  mountains  to  the  Lammermuir
hills,  in  which  the  following  relations  of  the  various
formations  are  shown.
The  gneissic  rocks  of  the  Grampian  mountains  (No.
