HORNBLENDE  FROH  THE  BIXXEXTBAL. 
Ill 
Vol.  49.] 
couple  of  hundred  more  from  Scotland  and  other  ‘disturbed’  regions, 
the  majority  of  which  bear  marks  of  pressure,  often  considerable, 
sometimes  extreme ;  but  most  of  them  testify  strongly  against  any 
subsequent  molecular  movement  of  importance1  ;  a  few  only  give 
some  hint  of  it,  and  these  two  specimens  are  the  first  in  which  the 
evidence  seemed  to  be  conclusive.- 
But  when  did  these  changes  occur?  Do  the  crushing  and  re¬ 
construction  both  date  from  Tertiary  times :  are  both  connected 
with  the  rise  of  the  present  Alps  ?  Upon  their  rocks,  no  doubt, 
the  record  of  that  grand  process  of  mountain-making  is  writ  in 
letters  bold  ;  but  may  not  this  be  even  as  a  palimpsest,  on  which  full 
often  the  earlier  characters  can  still  be  traced,  nay,  may  remain  some¬ 
times  almost  untouched  by  the  later  scribe  ?  Mountains  there  were 
on  the  site  of  the  Alps  at  the  beginning  of  Mesozoic,  even  in  Palteozoic 
ages.  The  fragments  in  the  Triassic  rauchwacke,  the  fragments  in 
the  Carboniferous  conglomerates  alike  exhibit,  in  their  cleavage- 
foliation,  a  record  of  earth-movements  by  which  their  parent  rocks 
had  been  already  modified.  The  former  at  any  rate  supply  materials 
for  comparison.3  In  the  rauchwacke  of  the  Yal  Piora,  the  Yal 
Canaria,  the  southern  opening  of  the  St.  Gothard  tunnel,  and  on  the 
flanks  of  the  Xufenenstock,  we  find,  among  other  rocks,  fragments 
of  a  rather  peculiar  mica-schist  (consisting,  according  to  Dr.  Gru- 
benmann,  chiefly  of  meroxene  and  margarite 4),  which  also  occurs 
in  situ  close  at  hand.  The  specimens  from  the  two  sources  only 
differ  in  this  respect,  that  those  from  the  parent  rock  show  more 
signs  of  crushing ;  they  have  been  once  oftener  than  the  others 
‘  through  the  mill.’  5  It  is  therefore  not  improbable  that  the&e 
more  important  changes  are  pre-Triassic,  even  pre-Carboniferous. 
But,  it  may  be  asked,  would  not  the  Tertiary  earth-movements  have 
again  crushed  or  sheared  the  rock-masses  and  so  distorted  or 
1  Contact-metamorphism  is  not  considered  as  a  cause,  though  of  course  it  is 
very  favourable  to  mineral  change,  because  there  is  nothing  in  the  structure  of  the 
rock  to  suggest  it,  nor  can  we  connect  the  change  with  the  possible  intrusion  of 
some  granitic  rocks  at  no  very  great  distance  from  one  of  these  localities.  Also 
I  do  not  rerkon  certain  hydrous  minerals,  or  such  ascalcite,  which  form  readily. 
2  The  aetinolite-schists  from  the  southern  side  of  the  St.  Gothard  Pass  afford 
the  nearest  parallels  to  the  rocks  now  described.  The  actinolites  are  irregular 
in  outline,  implicate  quartz,  etc.,  like  that  in  the  groundmass  (so  also  sometimes 
does  the  biotite),  and  are  not  seldom  associated  with  small  flakes  of  the  last 
mineral,  much  as  described  above,  as  if  the  biotite  either  had  formed  at  the 
expense  of  the  hornblende,  or  had  been  compelled,  in  a  simultaneous  crystal¬ 
lization,  to  acknowledge  its  suzerainty.  The  garnets  also  are  often  cleaved,  some¬ 
times  broken,  occasionally  crushed  ;  but  the  relation  of  the  crystal-building 
to  the  mechanical  disturbances  is  not  so  clear.  At  the  St.  Gothard,  however, 
the  evidence  of  the  garnets  suggests  that  the  amount  of  shearing  has  been  slight, 
so  the  actinolites  might  represent  older  crystals,  not  very  different  in  position. 
3  As  it  happens,  the  Carboniferous  conglomerates,  where  I  have  examined 
them,  have  lain  among  gneisses  and  schists  of  a  different  type  from  those  of  the 
group  described  in  this  paper. 
4  The  Disthcn-Schiefer  of  von  Fritsch.  The  rock  is  noticed  in  Quart,  Journ. 
G-eol.  Soc.  vol.  xlvi.  (1890)  pp.  226-228,  where  Dr.  Grubenmann's  exhaustive 
investigation  is  quoted. 
5  The  enclosed  fragments  would  he  saved  by  the  soft  friable  rauchwacke 
from  suffering  much.  Their  shapes  and  the  position  of  their  structure-planes, 
lying  at  all  angles  in  a  block  of  rauchwacke,  show  that  they  did  not  become 
foliated  after  being  detached  from  the  parent  rock. 
