Filler.]  INDIAN    VALLEY     REGION,    CALIFORNIA.  49 
which  characterizes  the  broad  summit  of  the  northern  end  of  the 
Sierra  Nevada.  The  pebbles  in  the  gravel  where  best  exposed  incline 
to  the  southwest,  indicating  the  course  of  a  stream  that  flowed  during 
the  gravel  period  from  near  Haskell  Peak  northward  by  the  Cascade 
mine  and  Peale's  and  Taylor's  diggings  to  Moonlight,  where  it  entered 
a  shallow  lake  that  covered  the  whole  of  that  portion  of  the  Sierra 
summit  as  far  south  as  Thompson  Peak.  Other  streams  flowed  into 
the  lake  from  the  south,  and  carried  into  it  at  first  chiefly  sand  and 
finally  a  great  mass  of  gravel,  which  now  covers  many  square  miles 
to  a  depth  of  hundreds  of  feet,  forming  the  largest  continuous  body 
of  auriferous  gravel  now  known  in  the  Sierra  Nevada.  In  the  lower 
portion  of  this  deposit  sand  prevails,  and  in  the  upper  half  gravel, 
often  coarse,  but  always  well  rounded  and  smooth.  Interstratified 
with  the  gravel  are  layers  of  sand,  frequently  containing  leaves  of  a 
flora  belonging  to  a  much  lower  altitude  than  that  at  which  they  are 
found  to-day.  Since  then  the  Sierras  have  been  uplifted  along  a 
fault  which  has  cut  the  gravel  as  far  north  as  Diamond  Peak,  leaving 
a  ridge  of  it  on  the  very  crest,  but  north  of  Diamond  Peak,  where  the 
range  dies  out,  the  gravel  bends  down  over  the  eastern  slope  and  is 
completely  indurated,  converting  it  into  a  solid  conglomerate. 
Much  of  the  gravel  of  this  great  field  is  too  firmly  cemented  to  be 
mined  by  ordinary  means.  There  are,  however,  large  masses  loose 
enough  to  be  easily  mined  b}^  water  delivered  under  pressure.  The 
chief  difficulty  is  the  lack  of  water  at  this  high  level. 
Bull.  260-05  m 4 
