310  PRE-CAMBRIAN    ROCKS    OF    NORTH    AMERICA.  [bull.  86. 
greater  part,  conform  to  the  surrounding  system  of  folds,  showing  it  as 
a  whole  to  be  an  indigenous  mass.  Two  observers  thus  approaching 
such  a  mass  would  justly  render  different  verdicts  as  to  its  nature,  one 
ascribing  to  it  a  wholly  eruptive  origin,  the  other  a  clearly  metamor- 
phic  character.  A  few  minor  masses  of  granite  did  not  show  well 
marked  transitions  from  schists,  though  in  part  the  ends  of  the  latter 
gradually,  yet  abruptly,  merged  into  the  granite,  as  if  absorbed 
by  it,  the  mass  as  a  whole  presenting  an  intrusive  character.  There 
is,  however,  no  evidence  whatever  to  show  that  such  masses  have 
traveled  far  or  that  they  might  not  have  come  from  a  short  distance 
only  and  have  been  derived  from  rocks  similar  to  those  in  which 
they  are  inclosed  or  others  of  the  same  series,  for  their  likeness  may 
be  found  at  other  points  as  true  metamorphics.  Penetrating  various 
portions  of  the  series  are  granitic,  usually  mostly  feldspathic,  veins, 
many  of  which  probably  extend  long  distances  and  appear  to  be  of 
true  eruptive  character,  while  other  granitic  veins,  usually  of  very 
coarse  bluish  quartz  and  white  cleavable  feldspar,  with  sheets  and 
large  crystals  of  white  mica,  seem  to  be  more  naturally  referred  to 
infiltration  or  to  be  endogenous  in  character,  like  many  metalliferous 
veins,  some  of  each  kind  showing  layers  of  dej)osition  or  structure. 
While  it  is  exceedingly  difficult  to  obtain  structural  results,  a  map  of 
the  eastern  slope  of  the  Front  range  is  presented.  The  portion  in  which 
the  structure  is  most  clearly  made  out  is  that  south  of  South  Clear  creek 
and  having  mount  Evans  as  its  culminating  point.  The  granite  of 
mount  Evans  occupies  as  low  a  geological  position  as  any  rocks  in  the 
range.  No  special  facts  bearing  on  the  equivalency  of  the  metamor- 
phic  series  to  any  of  the  divisions  of  the  Archean  of  the  east  were  ob- 
served. 
Peale,42  in  1874,  describes  several  sections  in  the  Front  range  at 
Pleasant  park,  glen  Eyrie,  Bergen  park,  and  Trout  creek,  in  all  of  which 
the  granite  underlies  the  fossiliferous  series.  On  the  South  Platte,  at 
the  change  from  the  sandstone  to  the  granite  the  former  contains  frag- 
ments of  unchanged  granite.  In  other  places  the  sandstone  appears  to 
pass  by  gradations  into  the  granite.  Pikes  peak  is  composed  of  fine' 
grained,  reddish  granite,  the  origin  of  which,  whether  eruptive  or  met- 
amorphic,  is  a  question.  On  the  road  from  Colorado  springs  to  South 
park  is  a  granitic  ridge  which  seems  to  be  thrown  up  through  the  coarse 
beds  which  lie  about  it.  In  the  range  of  the  South  park  several  sec- 
tions of  the  fossiliferous  series  are  described  which  rest  upon  granite 
or  gneiss.  At  Georgia  pass  eruptive  granite  forms  the  peak,  while 
black  micaceous  gneiss  is  at  the  base  of  the  series,  there  being  between 
the  two  slates  and  quartzites.  At  several  of  the  sections  given  the 
basal  layer  of  the  series  is  a  quartzite. 
Endlich,43  in  1874,  describes  granite  as  forming  the  heaviest  mass  of 
rock  north  and  east  of  the  Arkansas  and  south  of  the  line  running  east 
and  west  6  miles  south  of  Pikes  peak.     Upon  Cottonwood  creek  the 
