INTRODUCTION.  9 
series  was  commenced  in  1902,  and  the  papers  are  distributed  in  the 
same  manner  as  are  the  bulletins. 
4.  Monographs. — This  series  consists  of  cloth-bound  quarto  vol- 
umes, and  is  designed  to  include  exhaustive  treatises  on  economic  or 
other  geologic  subjects.  Volumes  of  this  series  are  sold  at  cost  of 
publication. 
5.  Geologic  folios. — Under  the  plan  adopted  for  the  preparation  of 
a  geologic  map  of  the  United  States  the  entire  area  is  divided  into 
small  quadrangles  bounded  by  certain  meridians  and  parallels,  and 
these  quadrangles,  which  number  several  thousand,  are  separately 
surveyed  and  mapped.  The  unit  of  survey  is  also  the  unit  of  publi- 
cation, and  the  maps  and  descriptions  of  each  quadrangle  are  issued 
in  the  form  of  a  folio.  When  all  the  folios  are  completed,  they  will 
constitute  a  Geologic  Atlas  of  the  United  States. 
A  folio  is  designated  by  the  name  of  the  principal  town  or  of  a  prom- 
inent natural  feature  within  the  quadrangle.  Ii  contains  topo- 
graphic, geologic,  economic;  and  structural  maps  of  the  quadrangle, 
and  in  some  cases  other  illustrations,  together  with  a  general  descrip- 
tion. 
Under  the  law  copies  of  each  folio  are  sent  to  certain  public  libraries 
and  educational  institutions.  The  remainder  are  sold  at  25  cents 
each,  except  such  as  contain  an  unusual  amount  of  matter,  which  are 
priced  accordingly. 
Circulars  containing  lists  of  these  folios,  showing  the  locations  of  the 
quadrangle  areas  they  describe,  their  prices,  etc.,  are  issued  from  time 
to  time,  and  may  be  obtained  on  application  to  the  Director  of  the 
United  States  Geologica.1  Survey.  The  following  list  shows  the  folios 
issued  to  date  and  the  economic  products  discussed  in  the  text  of 
each,  the  products  of  greatest  importance  being  printed  in  italic. 
List  of 
geologic  folios 
,  shoiving  mineral  resources 
described. 
No. 
Name  of  folio. 
State. 
Area 
in 
sq.m. 
Author. 
Mineral  products  described 
as    occurring    in    area    of 
folio. 
1 
Mont 
3,354 
980 
932 
969 
932 
975 
932 
975 
465 
925 
938 
Iddings,  J.  P.;  Weed, 
W.H. 
Hayes,  C  W 
Gold,    copper,    clays,    lime, 
stone,  coal. 
Coal,  iron,  manganese,  lime, 
?, 
Ringgold 
Ga.-Tenn 
Cal 
Tenn 
Cal 
Tenn 
Colo 
Tenn 
Colo 
Va.-W.   Va.- 
Md. 
Cal 
3 
Placerville 
Lindgren,     W.;  Tur- 
ner, H.  W. 
Hayes,  C  W 
clays,  stone,  road  metal. 
Gold,    copper,     quicksilver, 
4 
Kingston 
chromite,  stone. 
Coal,  iron,  lime,  stone,  road 
5 
Sacramento 
Chattanooga 
Pikes  Peak 
metal,  clay. 
Gold,  copper,  chromite,  iron, 
coal,  stone,  lime,  clay. 
6 
Hayes,  C  W.. 
7 
Cross,  W 
metal,  clay. 
Gold. 
8 
Sewanee 
Hayes,  C  W.... 
9 
10 
Anthracite-Crested 
Butte. 
Harpers  Ferry 
Jackson  
Emmons,  S.  F.;  Cross, 
W.;Eldridge,  G.H. 
Keith,  A 
metal,  clay. 
Coal,    silver,    gold,    stone, 
lime,  clay. 
Iron,  ocher,  copper,   stone, 
road  metal,  lime,  cement, 
rock. 
Gold,  copper,  chromite,  iron, 
manganese,    ocher,    coal, 
stone,  lime,  clay. 
11 
Turner,  H.  W 
