Vol.  49.]  GRANITE  IN  THE  GABBRO  OE  THE  CUILLIN  HILLS.  179 
Very  sparsely  scattered  through  this  groundmass  are  small  pheno- 
crysts  of  augite  and  olivine,  seldom  more  than  1*5  millimetre  in 
length,  the  former  sometimes  exhibiting  the  hour-glass  structure, 
and  the  latter  forming  interpenetrant  twins.  The  rock  is  so  poor 
in  alumino-alkaline  silicates  that  it  approaches  an  augitite  in  com¬ 
position. 
Very  great  interest  attaches  to  this  rock  from  the  circumstance, 
pointed  out  by  Herr  Sauer,  that  it  contains  inclusions  of  pyrrhotite 
(magnetic  iron-pyrites)  and,  in  addition,  one  fragment,  the  size  of 
a  walnut,  of  native  iron  covered  by  an  oxidized  crust.  This  iron  is 
perfectly  malleable  and  of  a  tin-white  colour,  but  it  does  not  exhibit 
the  Widmanstatten  figures  when  etched.  The  mode  of  occurrence 
of  iron  in  this  basalt  appears  to  resemble  that  in  the  basalt  of 
Ovifak  and  other  localities  in  Greenland,  and  those  of  the  nickel- 
iron  alloys  of  Vew  Zealand  (Awaruite)  and  of  Oregon  (Josephinit.e). 
The  basalt  of  Ascherhubel  is  described  by  Herr  Sauer  as  being 
so  rich  in  inclusions  of  foreign  rock  that  it  is  scarcely  possible  to 
find  a  large  fragment  of  the  igneous  material  which  does  not  con¬ 
tain  one  or  more  foreign  fragments.  These  belong  in  part  to  the 
Planer-  and  Quadersandstein  and  in  part  to  the  underlying  4  por¬ 
phyry,’  while  the  formations  which  form  the  foundation  of  the  sur¬ 
rounding  country  are  also  represented :  all  these  rock-masses  having 
been  penetrated  and  replaced  by  the  basalt.  Among  the  foreign 
fragments,  those  of  the  4  porphyry’  are  most  numerous,  though  they 
are  generally  small  in  size.  They  are  for  the  most  part '  perfectly 
vitrified,  but  nevertheless  often  show  indications  of  the  characteristic 
structures  of  the 4  porphyry.’  The  whitish  grey,  dirty  violet,  or  reddish 
spotted  fragments  are  compact  or  bubbly,  and  near  the  basalt  are 
generally  bounded  by  a  greenish-coloured  seam  of  augite-microlites. 
On  the  surface  they  are  covered  with  a  thin  weathered  crust 
resembling  kaolin. 
On  a  microscopic  examination,  we  find  a  glass  with  distinct 
periitic  structure  and  colourless  or  brownish  spherulites.  This 
glass  contains  felspars  which  are  occasionally  still  recognizable,  and 
are  generally  changed  into  a  granular  substance  sometimes  acting 
uniformly  under  polarized  light ;  there  are  also  minute  crystals  of 
magnetite  with  particles  of  haematite,  and  more  rarely  crystals  of 
spinel.  Besides  the  glass  there  are  dull,  undefinable  patches 
representing  the  4  porphyry  ’  in  a  less  changed  condition.  Herr 
Sauer’s  description  so  completely  agrees  with  the  section  to  which  I 
have  referred  as  being  obtained  at  Preiberg  that  there  is  no  room 
for  doubt  as  to  the  origin  of  the  specimen  from  which  it  was  cut. 
I  have  noticed  at  some  length  the  enclosures  at  Ascherhiibel,  for 
here  we  have,  as  in  the  Cuillin  Hills,  masses  of  acid  plutonic  rocks 
entangled  and  altered  by  a  magma  of  basic  material.  In  this  rock, 
as  in  the  cases  so  well  described  by  Prof.  Bonney  from  the  Island 
of  Arran,  we  get  clear  proof  that  not  only  are  characteristic 
alterations  produced  in  the  porphyritic  crystals,  but  that  spherulitic 
structures  are  develoDed  in  the  groundmass  of  such  acid  rocks  when 
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