330 
ME.  Gr.  BARROW  OX  AX  IXTRT7SIOX 
[Aug.  1893, 
29.  On  an  Intrusion  of  M uscovite-biotite  Gxeiss  in  the  SOUTH¬ 
EASTERN  HIGHLANDS  of  SCOTLAND,  and  its  ACCOMPANYING  MeTA- 
morphism.  By  George  Barrow,  Esq.,  E.G.S.  (Communicated 
By  permission  of  the  Director-General  of  the  Geological  Survey. 
Bead  March  22nd,  1893.) 
[Plates  XV.  &  XVI.] 
Contents. 
I.  Introduction  . 
II.  Distribution  and  Mode  of  Occurrence  of  the  Igneous  Eocks 
III.  Petrological  Characters  of  the  Igneous  Eocks  . 
IV.  Minerals  of  the  Metam orphic  Eocks  . 
V.  Eocks  of  the  Metamorphic  Area . 
(a)  The  Sillimanite-zone. 
( b )  The  Cyanite-zone. 
(e)  The  Staurolite-zone. 
VI.  Sedimentary  Origin  of  the  Metamorphic  Eocks  . 
VII.  Evidence  of  Progressive  Metamorphism . 
VIII.  GTeneral  Conclusions,  and  Summary  of  Eesults . 
IX  Analyses  of  the  Eocks  . . 
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I.  IXTRODECTIOX. 
The  area  to  which  attention  is  directed  in  the  following  pages  lies 
in  the  north-eastern  corner  of  Eorfarshire,  and  forms  part  of  the 
singularly  flat  table-land  of  the  South-eastern  Highlands.  It  is 
essentially  a  moorland  district,  much  covered  with  peat  and  heather, 
and  is  drained  by  two  rivers,  the  Horth  Esk  and  the  South  Esk. 
The  rocks  of  which  the  area  is  composed  consist  principally  of 
gneisses  and  schists  ;  these  are  clearly  seen  in  the  craggy,  sides  of 
the  vallej's  through  which  the  two  Esks  and  their  tributaries  flow. 
Boulders  of  these  rocks  may  be  noticed  in  the  rough  walls  by  the 
roadside  as  one  drives  up  the  glens,  and  their  intensely  crystalline 
aspect  is  a  most  striking  feature.  A  brief  visit  to  the  crags  and  the 
flat-topped  moorland  speedily  convinces  the  observer  that,  this 
crystalline  aspect  is  one  of  the  chief  characteristics  of  the  district. 
It  is  proposed  to  show  in  the  present  communication  that  this  area 
contains  several  masses  of  intrusive  rock  which  are  probably  con¬ 
nected  underground,  and  that  the  highly  crystalline  character  of 
the  surrounding  schists  is  mainly  the  result  of  thermometamorphism. 
II.  Distribetiox  axd  Mode  of  Occtjrrexce  of  the  Igneous  Bocks. 
The  normal  condition  of  the  intrusive  rock  is  that  of  a  slightly 
foliated  granite,  with  two  micas ;  but  there  are  considerable 
variations  from  this  type,  both  as  regards  structure  and  composition, 
as  will  be  seen  from  the  detailed  descriptions,  that  follow.  It  is 
met  with  in  masses  which  vary  greatly  in  size,  and  the  larger  of 
these  are  more  or  less  fringed  with  pegmatite,  veins  of  which  cut 
