INTRODUCTION. 
This  bulletin  is  an  extension  of  Bulletin  No.  100,  published  in  1893. 
In  that  work  were  catalogued  and  indexed  the  publications  issued  by 
the  Survey  from  the  date  of  its  organization  to  the  year  1892.  This 
work  brings  the  catalogue  and  index  to  date,  embracing  Annual 
Reports  1  to  21,  Monographs  I  to  XL  (except  Part  I  of  Monograph 
XXXII,  which  has  not  been  published),  Bulletins  1  to  176,  Water- 
Supply  and  Irrigation  Papers  1  to  45,  the  10  volumes  of  the  old  series 
of  Mineral  Resources  (1882-1893),  folios  1  to  70  of  the  Geologic  Atlas 
of  the  United  States,  the  completed  topographic  atlas  sheets  and  folios 
(about  1,100  sheets,  3  folios),  certain  special  maps  (general,  combined, 
forestry,  etc.),  and  miscellaneous  publications. 
The  first  portion  of  the  work,  the  catalogue,  is  much  more  abridged 
than  the  corresponding  portion  of  Bulletin  100,  bibliographic  details 
having  been  omitted.  The  index  has  not  been  materially  changed  in 
character.  It  is  intended  to  be  mainly  a  broad  classification  of  con- 
tents, alphabetically  arranged,  rather  than  a  full  index  composed 
largely  of  unrelated  items.  It  undertakes  to  put  the  inquirer  on  the 
proper  highway,  whence  in  most  cases  he  will  be  able  readily  to  iind 
the  place  he  seeks;  but  often  he  may  profit  by  a  consultation  of  the 
individual  volume  index  to  which  this  points,  which  should  give  him 
more  detailed  directions  for  finding  particular  places  along  diverging 
roads  and  lanes. 
The  index  has  been  in  preparation  many  months,  and  in  the  work 
the  writer  has  had  the  assistance,  during  intervals  in  their  regular 
work,  of  the  following  members  of  the  editorial  corps:  Mr.  F.  R. 
Rutter,  Mr.  L.  F.  Schmeckebier,  Mr.  W.  S.  Wiley,  Miss  M.  G.  Wil- 
marth,  and  Mr.  G.  M.  Wood. 
P.  C.  W. 
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