46  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
gravel  terranes  laid  down  during,  in,  and  after  the  glaciation,  were 
often  deposited  in  the  deep  fiords,  into  which  the  drainage  channels 
discharge.  There  are,  however,  some  post-Glacial  auriferous  gravels 
which  have  been,  and  are  being,  mined  at  a  profit. 
The  Juneau  placers  had  yielded  large  returns  long  before  a  stamp 
had  fallen  on  any  of  its  lode  ores.  In  the  Silver  Bow  basin  is  the 
oldest  placer  mine  of  the  region,  which  has  not  been  abandoned,  but  it 
was  not  in  operation  during  the  calendar  year.  A  comprehensive 
scheme  has  been  in  course  of  development  during  the  past  three  years 
to  hydraulic  the  gravels  of  the  Last  Chance  placer  mine.  This  prop- 
erty includes  a  gravel-filled  basin  on  Gold  Creek,  1  mile  from  JuneauJ 
A  tunnel  has  been  driven  for  half  a  mile,  through  which  it  is  proposed! 
to  hydraulic  the  placers.  As  yet  but  little  sluicing  has  been  done, 
difficulty  having  been  experienced  in  getting  rid  of  a  large  mass  of 
bowlders  at  the  upper  end  of  the  tunnel. 
Extensive  hydraulic  plants  have  been  installed  at  McGinnis  and 
Windfall  creeks,  northwest  of  Juneau.  Some  hydraulic  operations 
are  also  being  carried  on  at  Lemon  Creek,  10  miles  northwest,  and  at 
Windham  Bay,  75  miles  southeast  of  Juneau. 
The  Porcupine  is  the  largest  of  the  placer  districts  of  southeastern 
Alaska.  As  it  lies  close  to  the  International  Boundary  its  develop- 
ment has  been  retarded  by  the  uncertainties  of  control  of  a  part  of 
its  area.  It  is  expected  that  with  the  settlement  of  this  difficulty  itj 
will  now  take  a  new  lease  of  life.  A  description  of  this  district  by 
Mr.  Wright  will  be  found  elsewhere  in  this  report. 
YAKUTAT    BAY   REGION. 
This  region  would  not  here  be  worthy  of  mention  were  it  not  for' 
the  current  reports  of  the  discovery  of  new  placer  fields.  The  latest 
report  accredited  Yaktag  River  with  gold-bearing  gravels,  and  the 
rumors  have  been  sufficiently  definite  to  attract  some  prospectors.  It 
has  not  been  learned,  however,  that  these  prospects  are  of  any  com-' 
mercial  importance.  The  fact  that  gold  has  been  found  in  the  beach 
placers  at  Yakutat  and  Lituy a  bays,  where  it  apparantly  has  been  con 
centrated  from  glacial  material  by  wave  action,  points  to  the  conclusion 
that  there  are  gold-bearing  formations  somewhere  in  the  St.  Elias 
Range.  It  is  known  that  metamorphic  and  crystalline  rocks  do  occur 
in  this  range,  and  this  is  suggestive  of  the  conclusion  that  some  of  the 
auriferous  formations  of  southeastern  Alaska  find  their  extension  in 
these  high  mountains.  Additional  weight  is  given  to  this  point  of 
view  by  the  fact  that  the  western  extension  of  these  mountains  is  found' 
to  be  gold  bearing,  to  a  limited  extent  at  least,  along  the  lower  reaches1 
of  the  Copper  River  Valley  and  its  tributaries.  The  writer  does  not 
wish  to  convey  the  impression  that  this  range  will  necessarily  become 
a  locus  of  commercial  placers,  for  the  following  facts  would  argue 
