DIATOMACEOUS    DEPOSITS    IN    CALIFORNIA.  443 
is  fit   for  commercial  uses  or  altered  to  harder  varieties,  is  at  least 
4,500  feel . 
Hills  south  of  Santa  Rita. — Diatomaceous  deposits  covering  several 
square  miles  lie  on  the  southern  flanks  of  the  hills  south  of  Santa 
Rita,  the  series  attaining  a  thickness  of  several  hundred  feet  and 
being  finely  exposed  in  some  of  the  cliffs  on  the  north  side  of  Santa 
Ynez  River.  These  deposits  are  underlain  by  hard  shales,  and  it  is 
difficult  to  outline  areas  in  which  the  one  occurs  without  the  other. 
VICINITY    OF    SANTA    YNEZ. 
Hills  of  diatomaceous  earth  are  exposed  locally  about  H  miles 
northwest  of  the  Santa  Ynez  Mission  and  are  readily  seen  from  the 
valley  where  the  mission  stands.  The  shale  is  probably  of  consid- 
erable extent  here,  but  is  covered  for  the  most  part  by  thin,  geolog- 
ically recent  sand  deposits. 
Soft  shale  occurs  locally  3  miles  and  again  4  miles  southeast  of 
Santa  Ynez,  about  a  mile  north  of  the  river. 
VICINITY    OF    CASMALIA. 
The  hills  south  of  Casmalia  are  composed  of  white  diatomaceous 
shale  interbedded  with  slightly  brittle  layers  in  smaller  amount. 
The  canyon,  followed  by  the  road  due  south  of  Casmalia  over  to 
Burton  Mesa,  exposes  a  great  amount  of  pure  soft  earth  of  a  very 
good  quality.  This  extends  eastward  under  the  terrace  sands  and 
is  exposed  again  in  the  next  canyons  to  the  east.  The  sand  deposit 
is  not  deep,  and  the  tripoli  earth  is  very  near  the  surface  over  an 
area  of  5  to  10  square  miles. 
East  of  Casmalia  the  deposits  above  noted  continue  over  an  equal 
area,  being  covered  in  some  places  by  the  terrace  sand,  but  out- 
cropping in  all  the  canyons  and  forming  the  surface  over  the  greater 
portion  of  the  region.  A  good  quality  of  shale  is  exposed  along  the 
road  from  Casmalia  to  Harris  Canyon  and  on  the  ridge  north  of  it. 
Some  stretches  are  occupied  by  hard  or  impure  shale  that  is  unsuita- 
ble for  quarrying,  but  these  are  only  patches.  Material  of  an  espe- 
cially good  quality  is  exposed  in  large  amounts  on  the  southwestern 
flanks  of  the  ridge  running  southeastward  from  Schumann  toward 
Divide.  The  beds  in  general  are  only  gently  upturned  and  have  a 
thickness  amounting  to  many  hundred  feet. 
On  the  northeast  side  of  Schumann  Canyon  the  deposits  above 
mentioned  have  their  continuation.  In  the  low  hills  just  north  of 
Casmalia  diatomaceous  shale  of  rather  poor  quality  occurs,  but 
beginning  at  Schumann  and  running  northwestward  is  a  belt  of 
excellent  earth  on  the  southwest  side  of  the  high  ridge  bordering  the 
