Yol.  49.] 
HORNBLENDE  EEOjM  THE  BINNENTHAL. 
113 
perhaps  is  essential  to  it ;  so  also  will  a  high  temperature  :  possibly, 
when  the  resulting  structure  is  coarse,  it  too  is  no  less  essential. 
Altered  crystalline  rocks,  especially  crystalline  schists,  have  been 
produced,  unless  I  err  greatly,  in  more  than  one  way.  Nature,  in 
the  ages  of  the  past,  has  worked  ‘  at  sundry  times  and  in  divers 
manners.’  These  perchance  we  may  succeed  in  distinguishing  by 
means  of  the  careful  study  of  exceptional  cases,  especially  where 
something  is  known  as  to  the  origin  of  the  rocks. 
Discussion. 
The  President  believed  that  there  was  every  chance  of  the  rocks 
being  twisted  in  and  out  as  stated  ;  but  there  was  no  a  priori  impro¬ 
bability  in  the  occurrence  of  either  garnet  or  staurolite  in  Jurassic 
rocks,  or  in  rocks  of  any  age,  provided  the  necessary  materials  were 
there  and  the  conditions  suitable. 
Mr.  Eccles  remarked  upon  the  occurrence  of  two  series  of  horn- 
blendic  intrusive  rocks  in  the  black-mica  schists  and  gneisses  of  the 
Binn  district.  One  series — the  older  one — is  generally  interbedded 
with  the  surrounding  crystalline  rocks,  and  has  been  subjected  to 
the  same  pressure-modifications  as  the  latter.  The  dykes  of  the 
other  series  cut  across  the  foliation-planes  of  the  gneiss  and  schist, 
and  show  no  appreciable  cleavage.  No  instance  of  any  dyke  had 
been  observed  in  the  schists  and  Jurassic  beds  of  the  Nufenen 
district  by  Prof.  Bonney  or  the  speaker. 
Bev.  Edwin  Hill,  on  the  third  paper,  asked  if  there  were  any  ana¬ 
logy  in  the  crystals  which  do  not  disturb  fossils,  in  some  fossiliferous 
rocks — e.  g.  the  Schistes  d’ Angers  at  Ste.  Brigitte,  in  Britanny. 
Mr.  Rdtley  referred  to  a  case  in  which  the  schistose  banding  of 
a  rock  had  been  seen  to  pass  without  interruption  through  crystals 
of  staurolite. 
Mr.  Teall  also  spoke. 
The  Author  said,  in  reply  to  the  President,  that  what  might  be 
theoretically  possible  he  would  not  venture  to  affirm,  but  that,  as  a 
matter  of  fact,  no  Jurassic  rocks  in  the  Alps  had  authigenous  garnets 
and  staurolites,  and  all  rocks  with  these  minerals  could  be  proved  to 
be  far  earlier  than  any  Mesozoic  strata  :  to  Mr.  Eccles,  that  the  gneiss 
near  the  Hohsandhorn  might  prove  to  be  a  very  important  rock  in 
relation  to  the  geology  of  the  district.  As  regards  dykes  in  Mesozoic 
rocks,  he  had  never  seen  any,  so  far  as  he  could  remember,  in  the 
Central  or  Western  Alps.  With  reference  to  Mr.  Hill’s  remarks,  he 
pointed  out  certain  differences  between  the  case  of  contact-formed 
minerals  and  those  described  in  the  third  paper. 
a.  J.  G.  S.  No.  193. 
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