SURVEY  WORK  ON  WATER. 
In  addition  to  the  investigations  of  the  metallic  and  nonmetallic  resources  of  the  country, 
which  are  carried  on  by  the  geologic  branch,  the  Survey,  through  the  division  of  hydrology, 
has  also  made  extensive  studies  of  the  occurrence,  character,  and  economic  value  of  under- 
ground waters,  including  mineral  water  and  water  used  for  public,  industrial,  and  irrigation 
purposes. 
The  value  of  mineral  waters  sold  for  medicinal  and  table  purposes  alone  is  over  $10,000,000 
annually,  which  places  them  among  the  most  valuable  mineral  products  of  the  country, 
while  it  is  probably  safe  to  say  that  the  value  of  the  water  used  for  public  supplies  and  irri- 
gation is  more  than  that  of  all  other  mineral  products  combined. 
The  results  of  the  investigations  of  mineral  waters  are  published  in  a  series  of  reports  on 
"Mineral  Resources,"  which  appear  each  year,  while  those  dealing  with  all  other  classes 
of  water  are  issued  mainly  as  Water-Supply  and  Irrigation  Papers.  Occasionally,  however, 
important  papers  relating  to  waters  have  appeared  in  the  Geologic  Folios,  Bulletins, 
Annual  Reports,  and  Professional  Papers.  The  various  papers  on  underground  waters  may 
be  classed  as  follows : 
1.  Detailed  reports,  consisting  of  descriptions  of  the  occurrence,  quantity,  and  quality  of  the  under- 
ground waters  of  limited  areas.     Nearly  every  State  is  represented,  but  few  are  completely  covered. 
2.  Preliminary  reports,  containing  summaries  of  the  occurrence  of  underground  waters.  All  States 
east  of  Mississippi  River  and  a  number  of  those  west  of  the  river  have  been  covered. 
3.  Reports  on  mineral  and  potable  waters. 
4.  Reports  on  springs  and  spring  deposits. 
5.  Papers  on  artesian  requisites,  movements  of  ground  water,  etc. 
6.  Report  on  laws  relating  to  underground  waters. 
7.  Reports  on  measurements  of  flow  and  head. 
8.  Lists  of  wells  and  borings. 
In  addition  to  the  special  reports  on  underground  waters  a  large  number  of  Survey  papers 
on  other  subjects  contain  more  or  less  important  references. 
For  a  complete  classified  list  of  special  publications  on  underground  waters,  Water-Supply 
and  Irrigation  Paper  No.  160,  entitled  "  Underground-Water  Papers,  1906,"  should  be  con- 
sulted. A  full  subject  index  of  Survey  publications  on  ground  waters  up  to  the  beginning 
of  1905  will  be  found  in  the  "  Bibliographic  Review  and  Index  of  Papers  Relating  to  Under- 
ground Waters  published  by  the  United  States  Geological  Survey,  1879-1904,"  issued  as 
Water-Supply  and  Irrigation  Paper  No.  120. 
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