534  ME.  J.  POSTLETH  WAITE  ON  AN  INTKUSIVE  [Nov.  1893, 
quarry  near  the  summit  of  the  hill.  It  is  a  rock  of  somewhat  inter¬ 
mediate  character,  containing  much  felspar  and  a  little  quartz, 
slightly  porphyritic,  hut  very  rotten,  the  crystals  being  so  much 
decomposed  that  it  is  difficult  to  determine  what  they  have  been. 
One  or  two  suggest  a  pyroxenie  mineral,  hut  their  general  dirty 
look  accords  better  with  felspar.  There  are  also  some  grains  of  the 
clear  mineral  like  quartz  which  occurs  in  Slide  A.  The  rock  has  been 
slightly  affected  by  pressure. 
Slide  B  was  taken  from  the  diabase  at  Tarn  Nevin,  about  half-a- 
mile  from  the  eastern  end  of  the  intrusive  sheet.  It  is  a  finer- 
grained  and  seemingly  more  felspathic  rock  than  that  at  the  western 
end  of  the  sheet.  It  too  is  very  decomposed,  but  the  constituents 
are  generally  similar  to  those  of  the  former  rock  (Slide  A).  The 
pyroxenie  constituent,  however,  seems  to  have  been  less  in  pro¬ 
portion  ;  some  of  the  crystals  have  been  plagioclase.  It  is  difficult 
to  make  out  the  exact  structure,  but  it  is  more  probably  granular 
than  ophitic.  The  slide  was  taken  from  nearer  a  weathered  surface 
than  was  the  case  with  Slide  A. 
No.  1  is  the  opaque  white  quartz  associated  with  the  diabase  ;  it 
was  taken  from  the  head  of  the  old  shaft  near  Robin  Hood,  and 
seems  to  be  chiefly  vein-material,  quartz  with  rosettes  or  groups  of 
a  mica-like  mineral,  ahd  there  is  a  kind  of  chlorite,  also  some 
limonite,  but  not  quite  enough  of  the  matrix  to  be  sure  of  its  nature. 
It  has  been  a  little  affected  by  contact-action. 
Slide  4  was  taken  from  a  specimen  of  the  grit  obtained  in  an 
excavation  on  the  eastern  side  of  the  hill.  It  consists  of  fragmental 
quartz,  felspar  (much  decomposed),  mica,  and  possibly  a  little  tour¬ 
maline,  also  some  iron  oxide,  or  manganese.  The  slide  is  traversed 
by  a  quartz-vein.  There  are  no  signs  of  cleavage  or  contact- 
metamorphism. 
It  was  from  a  specimen  of  this  rock  that  Analysis  II.  (p.  533) 
was  made. 
Slide  3  was  taken  from  an  excavation  in  the  grit,  about  200  yards 
west  of  that  from  which  Slide  4  was  obtained.  It  is  a  fine- 
grained  grit  of  somewhat  similar  character,  but  with  some  rather 
distinct  indications  of  cleavage.  There  is  at  least  one  grain  of 
tourmaline  in  the  slide. 
In  the  middle  of  the  grit  at  this  point  there  is  a  thin  band  of 
slate,  and  from  this  band  Slide  6  was  taken.  The  rock  is  a  kind 
of  gritty  mudstone,  rather  schistose,  and  distinctly  cleaved.  The 
schistose  structure  seems  to  be  partly  due  to  contact-metamorphism, 
but  if  so,  the  appearances  are  in  favour  of  contact  first  and  pressure 
afterwards. 
Slide  5  is  from  a  specimen  of  soft  Skiddaw  Slate  obtained 
about  20  feet  north  of  the  diabase,  opposite  the  point  from  which 
Slide  2  was  taken.  The  slate  is  a  moderately  fine  mudstone 
containing  some  fragmental  mica,  other  constituents  being  much  as 
is  usual  in  such  rocks.  The  face  of  the  slate  roughly  coincides  with 
the  bedding,  the  cleavage  (not  very  strong)  cutting  it  at  a  high 
angle. 
