62  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
of  gold  in  the  gravel  beds.     These  high  benches  will  be  more  fully 
discussed  in  the  complete  report  on  this  placer  district. 
DEVELOPMENT. 
The  Porcupine  placer  diggings  date  from  the  summer  of  1898,  when 
they  were  discovered  by  three  prospectors  en  route  to  the  interior  over 
the  Dalton  trail.  After  the  rush  to  this  creek  in  1898  and  1899  there 
was  but  little  development  until  1900,  when  several  of  the  chim  hold- 
ers bonded  or  leased  their  properties,  while  others  formed  companies 
in  order  to  obtain  means  to  operate  on  a  large  scale.  The  peculiarities 
of  occurrence  here  require  a  still  further  combination  of  interests  for 
economic  exploitation,  and  negotiations  are  now  being  made  to  bring 
the  entire  creek  under  a  single  management.  The  only  claims  being 
developed  at  present  are  the  Cranston  and  Discovery,  on  Porcupine 
Creek,  and  the  Chisholm  and  Woodin  claims  on  McKinley  Creek.  To 
work  the  creek  gravels  it  is  first  necessary  to  divert  the  stream  into  a 
flume  built  to  one  side  of  the  channel,  then  to  install  a  derrick  to 
remove  the  large  granite  bowlders,  some  of  which  weigh  several  tons 
and  have  to  be  blasted.     After  this  a  hydraulic  plant  must  be  built. 
On  the  lower  claims  very  little  work  lias  been  done  owing  to  the 
depth  of  the  bed  rock.  The  first  property  worked  was  the  Cranston 
claim,  about  1  mile  above  the  mouth  of  the  creek.  Here  a  bench 
deposit,  which  is  said  to  carry  good  values,  is  being  hydraulicked  into 
a  sump  cut  into  the  bed  rock  10  feet  below  the  surface,  from  which  a 
bucket  elevator,  operated  by  water  power,  lifts  the  gravel  to  the  sluice 
boxes  above.  At  the  Discovery  claim  the  gravel  deposit  is  about  12 
feet  deep  and  is  reported  to  carry  high  values.  The  creek  has  beeij 
turned  through  a  large  flume  and  at  present  an  elevator  is  used  to  lift 
the  creek  gravels,  but  eventually  they  will  be  worked  through  ground 
sluices. 
On  McKinley  Creek,  an  eastern  branch  of  the  Porcupine,  which 
flows  in  a  canyon-like  valley,  the  beds  of  stream  gravel  are  very  nar- 
row. On  the  Chisholm  claim,  not  far  from  the  mouth  of  the  creek, 
the  placers  are  being  worked  by  the  ground-sluicing  method.  A  long 
flume  has  been  built  along  the  side  of  the  creek,  and  is  so  regulated 
that  the  water  can  be  turned  back  into  the  creek  channel  from  time  to 
time  and  the  smaller  gravels  washed  downstream,  thus  removing  tl  e 
upper  wash  and  concentrating  the  gold  in  a  shallow  deposit  on  lied 
rock  from  which  it  is  easily  recovered. 
The  operators  of  the  Woodin  claim,  one-half  mile  above  the  Chis- 
holm claim,  are  hydraulicking  a  bench  deposit  of  a  channel  150  feet 
above  the  creek.  One  troublesome  factor  here  is  the  occurrence  of  a 
capping  of  gravel  cement  3  feet  thick.  This  can  not  be  disintegrated 
by  the  hydraulic  nozzle,  which  throws  a  200-foot  stream  of  water, 
