868  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
Tyson,160  in  1850,  describes  sections  in  the  Sierra  Nevada  and  the 
Coast  Range.  The  rocks  are,  first,  metamorphic,  consisting  of  those 
of  sedimentary  origin,  such  as  slate,  but  subsequently  altered  by  the 
effects  of  heat;  and,  second,  of  hypogene  rocks,  which  include  granite, 
trap  rocks,  and  others. 
Blake,5  in  1856,  states  that  the  contorted  gneisses  of  the  Aquarius 
Mountains  are  metamorphic.  In  the  Aztec  Mountains  the  horizontal 
Carboniferous  strata  show  that  they  were  an  ancient  granitic  uplift. 
The  specimens  of  granite  are  of  a  red  or  rose  color,  few  or  none  being 
white  or  light  gray,  in  this  respect  contrasting  strongly  with  the 
collection  made  from  the  Sierra  Nevada  and  the  Bernardino  Sierra, 
as  well  as  from  those  of  the  Great  Basin  and  along  Mohave  River. 
The  metamorphic  rocks  are  in  all  probability  not  older  than  the 
Silurian  or  Carboniferous.  This  is  certainly  the  case  in  the  Aquarius 
Mountains.  In  the  rapid  reconnaissance  of  these  disturbed  and  meta- 
morphic rocks  it  was  not  possible  to  bestow  the  attention  upon  them 
which  their  obscured  condition  demands,  and  it  is  therefore  not  pos- 
sible to  assign  a  dividing  line  between  the  truly  erupted  granitic 
rocks  and  those  which  simulate  them  but  in  reality  are  of  sedimentary 
origin. 
Newberry,161  in  1856,  states  that  in  the  coast  mountains  are  found 
occasional  protrusions  of  granite  and  serpentine.  The  great  mass  of 
the  Sierra  Nevada  is  composed  of  plutonic  or  volcanic  rock,  granite, 
gneiss,  mica  schists  and  porphyries,  traps,  trachyte,  etc.,  with  aurifer- 
ous talcose  slates  and  veins  of  quartz.  The  western  slope  of  the  Cas- 
cade Mountains  in  one  place  where  crossed  is  composed  of  trappean 
and  metamorphic  rocks. 
Antisell,162  in  1856,  states  that  in  the  Coast  Range  the  igneous 
rocks  that  form  the  axis  are  of  two  kinds,  granitic  and  trachytic. 
Granitic  and  Primary  metamorphic  rocks  are  mentioned  as  occurring 
at  several  places  in  the  Coast  Range,  and  in  the  Cordilleras  in  many 
localities.    At  one  locality  hornblende  gneiss  is  found. 
Blake,163  in  1857,  states  that  granite  is  found  at  points  along  the 
coast  from  Monterey  to  near  the  Golden  Gate.  At  the  Tejon,  in  the 
Sierra  Nevada,  the  rocks  now  generally  classed  as  metamorphic,  such 
as  gneiss,  mica  schists,  hornblende  slate,  and  chlorite  slate,  are  pre- 
dominant. While  these  rocks  are  probably  a  metamorphosed  sedi- 
ment, the  linear  arrangement  of  the  minerals  is  not  regarded  as  satis- 
factory evidence  of  it.  This  structure  also  appears  when  the  rocks 
are  so  far  fused  as  to  obliterate  the  original  planes  of  stratification, 
and  therefore  the  words  strata  or  stratification  in  relation  to  these 
rocks  are  avoided,  but  to  designate  the  lines  or  layers  of  minerals 
the  terms  planes  of  structure  or  lamination  are  used.  At  one  section 
was  found  granite,  upon  both  sides  of  which  is  white  limestone ;  next 
to  the  latter  on  one  side  is  quartz  rock,  which  is  followed  by  chlorite 
