vanhise]  THE    CORDILLERAS.  309 
the  series  above.  A  similar  succession  was  observed  near  the  Little 
Thompson,  quartzites  being  found  at  the  top  and  granites  at  the  base. 
On  South  Saint  Vrain's,  and  at  the  mouth  of  South  Boulder  canyon 
are  found  quartzite  resting  upon  zoned  but  structureless  granite.  The 
Triassic  shales  rest  unconformable  upon  the  mica-schists  on  Little 
Thompson.  The  dominant  rocks  are  granitic  and  gneissic,  although 
Schists  are  found  over  large  areas,  and  of  these  the  tendency  is  toward 
a  binary  granite  to  which  the  name  Aplite  might  apply. 
That  the  characters  noted  above  are  evidence  of  a  structure  that 
once  existed  throughout  the  whole  mass;  that  the  inclosed  schistose 
patches  and  areas  are  neither  remnants  of  foreign  schists  inclosed  in 
an  eruptive  granite  mass,  nor  accidental  lamination  developed  by  crys- 
tallization or  motion  in  a  plastic  rock,  is  abundantly  proved  by  the  fact 
that  whenever  over  a  continuous  area  a  great  many  of  the  strikes  and 
dips  of  such  remnants  are  carefully  noted  and  platted  on  the  map,  they 
are  invariably  consistent  among  themselves  in  indicating  a  definite 
structure  of  the  whole,  and  accord  with  the  structure  that  may  be  in- 
dicated by  neighboring  schists  and  other  masses  of  undoubted  bedded 
rocks. 
As  in  the  derived  sedimentaries  is  found  the  debris  from  the  crystal- 
line rocks,  it  is  concluded  that  the  folding  which  affected  the  meta- 
morphism  is  older  than  that  which  has  upturned  the  sedimentary 
strata.  It  is  not  supposed  that  sufficient  heat  was  necessary  to  cause 
dry  fusion,  but  aqueo-igneous  fusion. 
While  metamorphism  alone  has  often  left  sharp  lines  of  demarkation 
between  differently  affected  rocks,  there  are  also  points  where  move- 
ments of  the  plastic  rock  seem  to  have  occurred;  while,  in  tracing  a 
line  of  schist  into  a  granite  area,  points  may  occur  where  the  normal 
granitoid  strata  regularly  belonging  to  the  series  may  gradually  in- 
crease in  number  and  thickness,  monopolizing  the  series  and  produc- 
ing a  normal  metamorphism ;  or  tongues  of  granite  may  invade  the 
schists,  as  if  an  active  metamorphism  had  proceeded  outward  from  the 
granites,  eating,  as  it  were,  into  the  schists,  and  absorbing  first  those 
beds  by  nature  most  readily  succumbing  to  the  change,  and  leaving 
Ithe  intercalated  masses  less  changed.    Yet  the  remnants  of  structure 
!eft  in  the  granites  still  show  that  no  important  movement  has  taken 
dace  in  the  mass,  but  that  the  rocks  remain  in  situ,  and  are  an  indigenous 
granite.  But,  besides  these  confusing  appearances,  lines  of  the  granite 
jjsometime  appear  as  if  actually  injected  or  intruded  among  the  schists, 
Sometimes  on  their  bedding,  and  perhaps  across  them  as  eruptive  veins. 
Indeed,  there  seemed  cases  where,  in  approaching  the  same  mass  of 
granite  from  different  points,  at  once  all  the  appearances  of  a  truly 
|xotic  and  eruptive  origin  might  be  found — abrupt  lines  of  demarka- 
tion and  veins,  while  at  another  point  nearly  all  the  steps  of  a  gradual 
jnetamorphisni  and  transition  from  the  schists  beyond  might  be  traced, 
vhile  the  remnants  of  structure  through  the  mass  itself  would,  in 
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