72  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1903.  [bull. 225. 
over  10  feet  of  muck  and  gravel.     Muck  may  constitute  a  half  of  this, . 
and  is  underlain  generally  by  a  light  wash,  and  this  by  a  sediment- 
bearing  gravel  in  which  the  gold  is  found.     The  gravel  is  composed 
mostl}r  of  quartzite-schist,   some  mica-schist,  gneiss,  and  occasional 
large  pieces  of  vein  quartz  up  to  a  foot  or  more  in  diameter. 
The  pay  dirt  is  said  to  run  from  2  to  7  feet  in  thickness  and  to 
contain  values  averaging  from  2  to  15  cents  to  the  pan.  The  gold  is 
generally  bright  and  occurs  in  granular  or  flattened  pieces,  some  of 
which  have  been  found  worth  $1.50. 
As  the  ground  is  deep  and  frozen,  prospecting  is  a  time-consuming 
task.  Holes  are  sunk  by  the  use  of  wood  fires,  hot  rocks,  and  hot 
water.  Sometimes  a  combination  is  used,  and  where  there  is  danger 
of  thawing  the  walls  too  rapidly,  hot  water  is  preferred.  It  is  diffi- 
cult to  thaw  much  more  than  2  feet  a  day  by  any  of  these  methods, 
and  their  use  means  an  expenditure  of  energy  far  in  excess  of  the 
results  attained,  yet  many  miners  are  forced  by  lack  of  capital  to 
work  by  these  methods,  and  much  patient  work  under  adverse  con- 
ditions is  being  accomplished.  One  boiler  with  steam  points  was  in 
operation;  another  had  just  reached  the  creek,  and  a  third  was  met  on 
the  way,  both  of  which  were  expected  to  be  in  operation  within  forty- 
eight  hours. 
With  the  advent  of  the  boiler,  work  can  be  done  more  easily  and 
quickly,  and  a  brief  description  of  the  method  may  not  be  out  of  place. 
Boilers  at  present  in  use  on  the  creeks  vary  from  2  to  6  horsepower,  and 
are  capable  of  supplying  steam  to  4  or  5  points.  Steam  is  generated  by 
the  boiler,  passes  through  an  ordinary  steam  pipe,  and  is  delivered  to 
the  points.  These  points  are  pipes  from  1  to  5  feet  in  length,  attach- 
able at  one  end  to  the  steam  pipe  and  at  the  other  end  provided  with 
a  small  opening  through  which  the  steam  rushes  with  greatly  increased 
penetrative  force.  They  correspond  to  the  nozzle  attached  to  fire 
hose,  and  the  whole  system  is  similar,  with  the  exception  that  the 
thawing  machine  is  adapted  to  the  transmission  of  steam  rather  than 
of  water.  The  blunt  ends  of  the  points  are  placed  in  position  against 
the  frozen  surface  and  the  steam  turned  on.  Shafts  may  rapidly  be 
sunk  to  bed  rock  by  this  method  and  the  ground  then  drifted  out 
laterally.  Care  must  be  exercised  to  prevent  the  too  extensive  thaw- 
ing of  the  ground  with  the  consequent  " sloughing"  or  falling  in  of 
material  from  the  walls. 
SUMMARY. 
The  creeks  above  described  are  the  only  ones  in  the  Fairbanks  dis- 
trict which  up  to  the  present  time  have  given  favorable  results.  The 
conditions  of  occurrence  on  all  of  them  are  essentially  the  same.  No 
foreign  wash  was  observed,  and  it  would  seem  that  the  gold  has  been| 
derived  from  the  rocks  in  which  the  creeks  have  cut  their  channels.  I 
