140  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1903.  [bull.  225. 
If  the  production  of  mineral  wealth  be  prolonged  sufficiently  for 
the  activities  of  the  community  to  be  directed  along  other  lines,  what 
was  once  a  mining  camp  may  become  a  permanent  settlement.  In  the 
Black  Hills  there  are  perhaps  two  features  which  may  operate  to  give 
to  the  region  a  greater  permanency  than  that  which  is  generally  seen 
in  communities  supported  solely  by  mining  interests.  The  first  is  the 
unusual  size  and  the  presumably  long  life  of  the  mines  of  the  Home- 
stake  belt.  The  second  is  the  gradual  decrease  in  the  cost  of  treatment 
of  other  grades  of  ore,  and  the  consequent  opening  of  the  market  to 
material  previously  known  but  hitherto  unworkable.  The  introduction 
of  the  cyanide  process  and  the  fact  that  large  quantities  of  low-grade 
ore  may  be  treated  by  its  use  have  done  much  to  extend  the  life  of 
Black  Hills  mining.  It  is  not  improbable  that  these  two  factors 
working  together  may  so  prolong  the  mineral  production  of  the  region 
that  the  population  may  never  be  less  than  it  now  is.  Other  interests 
which  grow  side  by  side  with  the  mining  industry  may  in  the  future 
become  so  important  and  so  little  dependent  on  the  mineral  wealth  of 
the  country  that  their  existence  alone  will  be  sufficient  to  support  the 
cities  which  have  grown  up  in  this  mining  country. 
