GRAND   MESA   COAL  FIELD,    COLORADO.  317 
were  collected  from  the  various  coal  openings  for  analysis  and  for 
comparison  with  coal  from  other  fields,  and  data  were  collected  con- 
cerning the  characteristics  of  the  coal  that  might  affect  its  market 
value — such,  for  example,  as  its  tendency  to  slack  and  its  ability  to 
coke.  The  accessibility  of  the  coal  is  indicated  on  the  accompanying 
map  (PL  XXI),  which  shows  the  general  surface  configuration  of  the 
field  by  means  of  contour  lines. 
In  accordance  with  the  object  of  this  work,  an  attempt  was  made 
to  map  and  classify  the  land  by  townships,  ranges,  and  sections.  As 
the  work  progressed,  however,  it  was  found  that  the  land  surveys  were 
not  adequate  for  this  purpose.  In  the  lowlands  at  the  west  end  of 
the  field  almost  all  the  corners  were  found,  but  in  the  central  and  east- 
ern parts  few  could  be  located  in  the  lowlands  and  practically  none 
in  the  highlands,  where  the  coal  occurs.  The  presence  of  corners  is 
indicated  on  the  accompanying  map  by  solid  lines;  the  dotted  lines 
indicate  that  none  was  found. 
In  the  absence  of  Government  corners  near  the  coal,  some  other 
method  of  determining  location  had  to  be  devised.  In  many  places, 
because  of  the  precipitous  character  of  the  country,  it  was  impracti- 
cable to  traverse  the  outcrop  of  the  coal,  and  its  location  was  deter- 
mined principally  by  triangulation  from  such  corners  as  could  be 
found;  many  of  these  were  several  miles  away.  This  method  might' 
have  given  satisfactory  results  if  the  corners  used  in  triangulation  had 
been  accurately  located,  but  that  many  of  them  were  not  became 
evident  when  locations  of  certain  points  made  from  one  set  of  corners 
failed  to  coincide  with  locations  of  the  same  points  made  from  other 
corners.  Some  of  the  inaccuracies  are  traceable  to  the  original  sur- 
veys and  others  to  the  attempts  of  local  surveyors  to  reestablish  lost 
corners  or  to  establish  new  ones  where  they  supposed  the  original 
corners  should  be.  For  these  reasons,  although  the  map  is  approxi- 
mately correct,  no  final  classification  of  the  land  can  be  made. 
ACKNOWLEDGMENTS. 
The  writer  was  assisted  in  the  field  by  Charles  S.  Blair,  who  spent 
part  of  the  time  in  examining  the  coal  and  part  of  it  in  constructing 
the  map,  and  by  Russell  R.  Bryan,  whose  time  was  devoted  wholly 
to  mapping.  The  office  work  of  preparing  the  map  for  publication 
was  done  mainly  by  A.  J.  Hazlewood.  The  writer  also  wishes  to 
acknowledge  his  indebtedness  to  Alex  Bowie,  S.  G.  Porter,  and  other 
mine  owners  for  aid  and  many  courtesies  during  the  fieldwork,  and 
to  J.  W.  Curtis,  of  Delta,  who  furnished  much  information  regarding 
the  land  surveys. 
The  invertebrate  fossils  collected  during  the  investigation  have  been 
identified  by  T.  W.  Stanton  and  the  fossil  plants  by  F.  II.  Kno'wlton. 
On  their  identifications  depend  the  correlations  made  in  this  paper. 
