hayes.]  NONMETALLIFEROUS    ECONOMIC    MINERALS.  27 
is  now  preparing  a  voluminous  report,  which  will  be  published  during 
the  year  1904. 
In  connection  witli  his  investigation  of  the  cement  resources  Mr. 
Eckel  visited  numerous  slate  quarries  throughout  the  country  with  the 
expectation  of  making  a  systematic  examination  of  the  slates  of  the 
United  States  during  the  coming  year.  He  has  prepared  a  brief  account 
of  certain  slate  deposits  in  California  and  Utah  for  this  volume,  which 
also  includes  notes  on  Arkansas  roofing  slates  by  T.  Nelson  Dale. 
Clays  have  been  examined  in  many  localities  in  connection  with  the 
preparation  of  geologic  folios.  Important  deposits  have  been  exam- 
ined, particularly  in  Pennsylvania,  and  a  report  on  the  clays  of  the 
Ohio  Valley  in  Pennsylvania  has  been  prepared  for  this  volume  by 
L.  F.  Woolsey.  Investigation  of  clay  resources  has  been  made  by 
H.  E.  Gregory  in  connection  with  folio  work  in  the  Connecticut 
Valley,  and  by  Mr.  Fenneman  in  the  Boulder  district,  Colorado.  A 
systematic  examination  of  the  clays  of  Mississippi  has  been  undertaken 
in  cooperation  with  State  officials,  the  work  being  done  by  A.  F.  Crider 
under  Mr.  Eckel's  supervision. 
Gypsum,  salt,  sulphur,  etc. — A  systematic  summary  of  information 
relating  to  the  gypsum  deposits  of  the  United  States  has  been  made 
during  the  past  year  under  the  direction  of  George  I.  Adams.  Chap- 
ters on  the  deposits  of  the  various  States  have  been  contributed  to 
this  report  by  specialists  particularly  familiar  with  the  subject.  This 
report  is  now  in  press.  In  addition  to  summarizing  existing  informa- 
tion it  contains  a  large  amount  of  new  information,  the  results  of  per- 
sonal examinations  of  the  various  deposits  by  the  experts  employed  to 
contribute  the  several  chapters. 
The  salt  industry  of  Utah  and  California  has  been  investigated  by 
Mr.  Eckel  in  connection  with  his  work  on  the  cement  deposits,  and  a 
brief  report  has  been  prepared  for  this  volume.  Mr.  Adams  visited 
the  Rabbit  Hole  Sulphur  mines,  near  Humboldt  House,  Nevada,  and 
has  prepared  a  report  upon  the  geological  relations  and  development 
of  these  deposits.  In  connection  with  his  work  on  the  Silver  Peak 
quadrangle,  Mr.  Spurr  examined  the  natural  alum  deposits  in  Esmer- 
alda County,  Nev.,  and  has  prepared  a  brief  report  upon  them. 
Miscellaneous  nonmetalliferous  minerals. — The  fluorspar  deposits  of 
southern  Illinois  were  investigated  by  Mr.  Bain  in  connection  with 
his  studies  of  the  lead  and  zinc  deposits  of  the  Mississippi  Valley.  He 
has  reached  important  conclusions  regarding  the  relations  of  the  fluor- 
I  spar  and  the  associated  lead  and  zinc,  and  has  made  a  special  study  of 
I  the  development  of  these  deposits  in  their  commercial  aspects.  The 
deposits  of  graphite  in  the  eastern  Adirondack^  have  been  examined 
by  J.  F.  Kemp  in  connection  with  his  folio  work,  and  a  brief  report 
has  been  prepared  for  this  volume.  Deposits  of  barite  in  southern 
Pennsylvania  have  been  examined  by  G.  W.  Stose,  also  in  connection 
with  folio  work,  and  a  brief  report  has  been  prepared  for  this  volume. 
