hayes.]  INTRODUCTION.  17 
series  was  Mineral  Resources  of  the  United  States,  1882;  the  last, 
Mineral  Resources  of  the  United  States,  1893.  In  1894  this  form  of 
publication  was  discontinued,  in  accordance  with  an  act  of  Congress, 
and  the  material  was  included  in  certain  parts  of  the  sixteenth,  seven- 
teenth, eighteenth,  nineteenth,  twentieth,  and  twenty-first  annual 
reports.  The  separate  publication  of  the  series  on  mineral  resources 
was  resumed,  however,  in  1901,  in  accordance  with  an  act  of  Congress, 
and  three  volumes  of  the  new  series,  Mineral  Resources  of  the  United 
States  for  1900,  for  1901,  and  for  1902,  have  been  issued. 
This  publication  contains  a  systematic  statement  of  the  production 
and  value  of  the  mineral  products  of  the  United  States,  a  summary  of 
new  mineral  resources  developed,  and  occasionally  short  papers  on 
economic  geology,  when  necessary  in  accounting  for  the  new  develop- 
ments. 
Bull.' 225— 04 2 
