Richardson.]      SALT,    PETROLEUM,    ETC.,    TN 
presence  of  organic  matter,  and  at  other  places  it  is  stained  red  by 
iron  oxide.  Locally,  disseminated  selenite  is  abundant,  Some  sec- 
tions show  occasional  thin  beds  of  banded  gray  limestone  in  the  gyp- 
sum.    Deposits  of  native  sulphur  are  also  associated  with  it. 
The  thickness  of  this  formation  is  not  known,  but  it  is  consider- 
able. A  well  at  the  old  sulphur  works  about  6  miles  north  of  Rustler 
Springs  shows  a  thickness  there  of  a  little  over  300  feet,  though  the 
base  of  the  gypsum  is  not  known  to  have  been  reached.  Good  sec- 
tions, exposing  sometimes  50  or  GO  feet  of  gypsum,  occur  along  Dela- 
ware Creek  and  Cottonwood  Draw.  Such  sections  commonly  show 
the  rock  to  be  considerably  cracked  and  jointed. 
This  gypsum  is  also  cavernous,  and  there  are  many  underground 
channels  in  it.  A  conspicuous  one  heads  in  a  small  draw  about  G 
miles  southeast  of  Sayles's  ranch,  35  miles  northwest  of  Toyah.  The 
opening  of  the  cavern  is  circular,  with  a  diameter  of  about  5  feet, 
and  it  has  been  explored  for  a  distance  of  a  quarter  of  a  mile.  A 
peculiar  variety  of  bunch  grass  (Bouteloua  breviseta),  called  "  yeso  " 
grass,  grows  on  the  gypsum,  which  also  bears  a  stunted  growth 
of  junipers. 
