emmons]  INVESTIGATION    OF    METALLIFEROUS    ORES.  19 
which  cover  a  large  portion  of  western  Kansas,  contain  gold  in  paying 
quantities.  Those  who  claimed  to  have  obtained  the  best  results  by 
assa^y  admitted  that  a  large  proportion  of  their  tests  gave  no  values, 
but  accounted  for  these  negative  results  hy  assumed  imperfections  in 
modern  methods  of  assay.  Of  others  who  assayed  the  material,  few 
were  able  to  find  any  gold  whatever.  The  representations  of  the 
believers  in  the  occurrence  of  gold,  to  the  effect  that  the  shales  might 
be  treated  by  smelting  or  some  other  process  at  a  profit,  naturally 
appealed  to  the  imagination  of  those  who  owned  land  in  that  region, 
since  the  quantity  of  these  shales  on  their  land  is  practically  unlimited. 
With  a  minimum  estimate  of  profit  of  onbv  a  dollar  a  ton  one  might 
calculate  a  half  million  dollars  to  the  acre,  and  it  would  take  compara- 
tively few  square  miles  to  pay  the  national  debt,  as  there  was  no  rea- 
son for  assuming  that  one  part  of  the  shales  was  richer  than  another. 
It  seemed  highly  improbable,  however,  that  gold  could  be  extracted 
from  the  shales  at  a  profit  by  any  known  process,  even  if  they 
contained  as  much  gold  as  the  most  enthusiastic  advocates  claimed  for 
them. 
Mr.  Lindgren's  samples  (19  in  number)  were  taken,  and  the  assays 
(77)  were  conducted,  it  is  hardly  necessaiy  to  say,  with  great  intelli- 
gence, care,  and  accurac}^.  Their  results  showed  that  the  vast  majority 
of  the  samples  contained  no  trace  of  gold  whatever,  values  of  a  few 
cents  being  found  in  a  small  number  of  the  specimens,  which,  how- 
ever, could  not  always  be  found  on  a  repetition  of  the  assay. 
These  results,  though  convincing  to  the  scientific  mind,  do  not  nec- 
essarily affect  opinions  that  are  based  on  the  supposed  unreliability  of 
assay  methods,  though  Mr.  Lindgren  gives  good  scientific  reasons  why 
these  methods  are  the  most  reliable  for  determining  the  presence  or 
absence  in  rock  material  of  very  minute  amounts  of  the  precious  metals. 
The  final  test  will  necessarity  be  the  success  or  failure  of  practical 
attempts  to  treat  the  material  on  a  large  working  scale. 
Bulletin  219  is  a  preliminary  report  on  the  results  of  Mr.  Spurr's 
final  examination  of  the  Tonopah  district  of  Nevada,  which  he  com- 
pleted during  the  past  summer.  It  is  a  brief  summary,  notyet  checked 
by  final  microscopic  and  other  office  work,  intended  for  the  immediate 
use  of  those  engaged  in  mining  in  the  district. 
Under  the  system  of  free  distribution  recentty  ordered  by  Congress, 
the  first  edition  of  this  bulletin  was  exhausted  on  the  day  of  its  publi- 
cation.    The  report  is,  however,  reprinted  in  this  bulletin. 
ECONOMIC  PUBLICATIONS  IN   PREPARATION. 
Other  investigations  of  metalliferous  ores  which  have  been  brought 
to  completion  daring  the  past  year,  reports  of  which  will  soon  appear 
as  professional  papers,  are  as  follows: 
Professional  Paper  No.  12,  Ore  Deposits  of  the  Globe  District,  Arizona,  by  F.  L. 
Ransoine. 
