Vol.  49.]  ‘  GREENSTONES,’  ETC.,  EROH  THE  PENNTN'E  ALPS.  99 
dark  green  acicular  hornblende  and  a  grey  felspar-like  mineral  alter¬ 
nately  predominate,  and  contains  some  reddish  garnet  ingrains  about 
the  size  of  a  mustard-seed.  Under  the  microscope  the  first  mineral 
is  rather  strongly  coloured,  dichroic,  and  shows  the  characteristic 
cleavages :  most  of  the  second  proves  to  be  epidote.  There  is 
probably  a  little  interstitial  quartz.  The  garnets  appear  to  be 
original  constituents,  or  at  any  rate  anterior  to  the  pressure. 
The  last  specimen  is  representative  of  one  of  the  more  banded 
varieties  of  the  Hornblende-Schiefer  from  the  upper  part  of  the 
Riffelberg  (collected  a  few  hundred  feet  above  the  Hotel).1  The 
chief  constituents  are  actinolite,  a  rather  strong  green  hornblende  in 
somewhat  irregular  ill-formed  prisms,  evidently  replacing  glauco- 
phane,2  which  still  remains  in  places,  and  epidote,  with  some  reddish 
garnets  and  white  mica.  The  rock  is  but  slightly  fissile  and  is 
somewhat  foliated. 
To  sum  up  :  it  is  certain  that  one  of  the  groups  described  above 
is  of  igneous  origin ;  it  is  highly  probable  that  the  other  is  the 
same,  and  that  pressure  has  been  a  most  important  if  not  the  main 
agent  of  change.  The  original  structure  is  lost ;  the  constituents 
to  a  great  extent  (if  not  altogether)  have  entered  into  new  com¬ 
binations  ;  a  considerable  quantity  of  biotite  (or  chlorite)  and  of 
hornblende  has  been  formed,  and  the  last-named  mineral  is  more 
or  less  acicular  in  habit. 
Tor  the  next  set  of  specimens  I  am  indebted  to  my  friend  Hr. 
Eccles,  but  my  general  knowledge  of  the  district  from  which  they 
come  enables  me  to  affirm  that  the  rocks  in  which  they  are  intrusive 
belong  to  the  great  calc-mica-schist  group  already  mentioned.3 
The  first  specimen,  from  the  Tschampigel  Keller,  near  Binn,4  is  a 
somewhat  foliated  dark-green  hornblendic  rock,  faintly  speckled 
with  grey  and  white.  Under  the  microscope  a  rather  dull-green 
hornblende  is  seen  to  be  the  most  abundant  mineral.  It  usually 
occurs  in  prisms  about  6  or  7  times  as  long  as  broad,  ranging  from 
about  -07  inch  to  mere  belonites,  from  *03  inch  to  *04  inch  being  a 
common  length  ;  the  larger  grains  exhibit  the  characteristic  cleavage, 
but  their  faces  generally  are  not  well  developed.  Biotite  is  fairly 
1  I  have  in  my  collection  specimens  (unsliced)  of  the  Grilner  Schiefer  from 
the  neighbourhood  of  Zermatt,  the  flank  of  the  Hornli,  and  the  Furggen-grat, 
and  do  not  see- how  to  separate  them  either  from  the  last-named  or  from  others 
described  above. 
2  Boulders  of  a  slightly  foliated  rock  rich  in  glaucophane  are  rather  common 
in  the  Saasthal,  and  evidently  come  from  the  mountains  enclosing  the  Ailalin 
and  Hochlaub  glaciers. 
1:5  They  are  generally  dark-mica  schists,  sometimes  calcareous,  occasionally 
interbedded  with  white  crystalline  limestone  or  dolomite.  For  description,  see 
Quart.  Journ.  Geol.  Soc.  vol.  xlvi.  (1890)  pp.  199-204. 
4  From  a  rather  irregular  dioritic  dyke  which  breaks  through  the  black- 
garnet  schists,  irrespective  of  their  bedding.  It  varies  from  5  to  20  feet  in 
thickness,  is  rather  massive,  and  shows  externally  little,  if  any,  evidence  of 
schistosity.  Striking  (roughly)  E. Is. E.-W.X.W  .,  it  does  not  appear  to  extend 
far,  but  is  probably  connected  with  a  larger  mass  of  similar  rock  which,  however, 
is  interbedded  like  a  sill  between  the  garnet-schists. — J.  Eccles. 
