Yol.  49.]  4  GREENSTONES,’  ETC.,  FROM  TEE  PENNINE  &.LPS. 
97 
that  it  was  formerly  a  basalt  or  dolerite  can  hardly  he  doubted,  of 
which  condition  practically  not  a  trace  remains.1 
The  next  specimen  is  from  the  north  side  of  the  eastern  flank  of  the 
Mittaghorn.2  Here  a  group  of  dykes  (about  a  dozen  in  all,  one  or 
two  branching)  cut  the  calc-schist,  above  which,  at  no  great  distance, 
is  gneiss.  Commonly  these  dykes  are  about  six  inches  thick ;  the 
largest  has  a  thickness  of  about  half  a  yard.  Similar  dykes  can  be 
traced  some  little  distance  up  the  mountain-side,  both  in  the  calc- 
schist  and  in  the  gneiss.  They  have  been  sometimes  folded  wjth  the 
calc-schist :  their  relation  to  the  foliation  of  the  gneiss  is  not  so  clear.3 
The  specimen  examined  is  a  dull  greyish-green  rock,  slightly  fissile, 
with  a  faint  silvery  sheen  on  the  irregular  divisional  surfaces.  Under 
the  microscope  the  constituents  are  seen  to  be  the  same  as  in  the 
last-described  rock,  but  there  is  rather  less  epidote,  more  biotite,  the 
4  chlorite  ’  is  slightly  deeper  in  colour,  and  actinolite  is  more  frequent.4 
The  constituents  are  rather  smaller,  and  the  structure  of  the  rock 
is  a  little  more  suggestive  of  crushing. 
The  third  specimen  is  from  a  dyke  obviously  much  affected  by 
pressure,  from  1  to  2  yards  wide,  cutting  calc-schist,  on  a  shoulder 
of  the  Fee-Gletscher  Alp,  near  the  right  bank  of  the  left  arm  of  the 
Fee  Glacier.5  The  specimen  examined  is  a  rather  fissile  greyish- 
green  rock,  with  a  slightly  silvery  sheen  on  the  cleavage-surfaces. 
1  This  identification  is  confirmed  by  an  analysis  kindly  made  for  me  by 
Mr.  A.  A.  Longsden  in  the  chemical  laboratory  at  University  College,  London. 
After  treatment  with  dilute  HC1  for  about  24  hours,  8'99  per  cent,  of  the  rock 
proved  to  be  soluble,  and  was  thus  composed  : — FeO  =  1"63,  CaO  =  3"87,  MgO 
=  057,  002  =  2'92.  The  residue  gave  Si02  =  43"70,  A1203  =  23'44,  Fe003 
=  3T4,  FeO  —  3'64,  CaO  =  9T8,  MgO  =  2  ”97  (probably  slightly  too  high), 
]Sa90  :  -  4*86,  H20  =  2"40  (combined) : — Total  —  93'33.  Combining  the  two 
results  for  a  bulk  analysis,  the  composition  is : — 
Si02 
43-70  ) 
ai2o3 
23-44 
Fe.,03 
:  - 
3-14 
FeO 
5-27 
CaO 
13-05 
MgO 
— 
3-54  y 
Na.,0 
7- 
4-86 
h.2o 
= 
2-40 
co2 
2-92 
102-32  ; 
The  rather  high  percentage  of  lime  may  be 
accounted  for  by  some  infiltration  of  calcium 
carbonate  from  the  neighbouring  calc-schist,  but 
the  analysis  on  the  whole  fairly  represents  a  some¬ 
what  decomposed  basalt. 
2  Somewhat  lower  down  than  the  last  locality,  where  the  track  is  running 
nearly  on  a  level. 
3  Perhaps  I  should  mention  that  in  the  Alps  the  date  of  the  cleavage- 
foliation  is  not  so  readily  determined  as  might  be  supposed.  Their  rocks  were 
greatly  affected  by  the  earth-movements  to  which  the  present  chain  is  due,  i.  e.  of 
Tertiary  age,  but  there  is  evidence  that  a  cleavage-foliation  existed,  at  any  rate 
in  some  parts,  in  pre-Triassic  or  even  pre-Carboniferous  times. 
4  There  are  some  microliths  of  rutile  or  possibly  pseudobrookite. 
5  Across  a  shallow  depression  is  a  larger  mass  of  ‘  green  schist  ’  with  which  the 
dyke  is  probably  connected.  About  20  yards  from  it  is  a  mass  of  serpentine, 
which  throws  off  a  dyke  cutting  the  calc-schist. 
Q.J.G.S.  Ho.  193. 
H 
