260  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904."        [bull.  26oj 
zontal  plane.  For  the  present  prospecting  is  carried  on  only  with  the 
drill,  and  in  the  inception  of  each  enterprise  the  prospecting  is  essen- 
tially blind.  There  are  at  present  seven  companies  in  St.  Francois 
County  and  three  in  Madison  County  which  are  outputting.  A  num- 
ber of  others  have  not  yet  reached  the  producing  stage.  There  is  a 
very  large  area  of  unprospected  territory  of  possible  value,  but  in  the 
present  condition  of  knowledge  the  heavy  charge  incident  to  the  pre- 
liminary drilling  of  this  ground  prevents  the  rapid  opening  of  more 
mines. 
In  Washington  and  Franklin  counties,  north  and  west  of  the  dis- 
seminated lead  district,  galena  occurs  in  intimate  association  with 
blende  and  barite  in  the  Potosi  formation.  The  ore  occurs  in  crevices 
and  flats  in  many  particulars  similar  to  those  of  Wisconsin.  The 
individual  ore  bodies  are  not  large,  and  the  workings  are  shallow.  In 
the  aggregate,  however,  the  area  has  yielded  a  considerable  amount  of 
lead,  and  a  small  output  is  steadily  maintained.  Somewhat  similar 
ore  bodies  extend  Avell  into  central  Missouri,  and  those  of  Miller 
County  have  recently  been  described  by  Messrs.  Ball  and  Smith.0 
Economically  they  are,  for  the  present,  at  least,  unimportant.  It  is 
interesting  to  note  that  the  contrast  of  these  deposits  with  those  of 
St.  Francois  and  Madison  counties  in  character  and  form  of  ore  body 
and  in  the  mineralogical  association  of  the  galena  is  coincident  with 
a  change  in  the  formation  which  constitutes  the  country  rock. 
In  Missouri,  as  in  the  other  States  producing  soft  lead,  the  ore 
bodies  show  no  association  with  igneous  rocks  or  even  with  markd 
disturbance  of  the  strata.  In  general  they  are  instead  associated 
with  relatively  undisturbed  sedimentary  rocks.  In  most  cases  the] 
country  rock  is  dolomite  or  magnesian  limestone. 
FUTURE  PRODUCTION  OF  LEAD. 
The  consumption  of  lead,  both  in  this  country  and  abroad,  has  beei 
steadily  increasing  for  some  years.  It  is  to  be  expected  that  it  will 
continue  to  do  so.  In  the  United  States  the  price  has  not  shown  an^ 
very  direct  relation  to  the  increase,  as  is  seen  from  the  table  following : 
a  Ball,  Sidney  II.,  and  Smith,  A.  F.,  Geology  of  Miller  County,  Missouri :  Bureau  Geol. 
and  Mines,  Bull.  vol.  1,  2d  ser.,  1903,  207  pp. 
