landes.]  CLAY    DEPOSITS    OF    WASHINGTON.  557 
erals  have  been  thoroughly  decomposed  and  their  soluble  constituents 
been  lost  by  leaching.  Pits  have  been  opened  in  the  decayed  granite 
to  a  depth  of  15  feet  or  more,  and  the  rock  to  this  depth  is  sufficiently 
soft  to  be  easily  removed  with  pick  and  shovel.  Adjacent  to  the 
residual  clay  and  sand  deposits  are  beds  of  clay  which  are  with- 
out doubt  of  granitic  origin,  but  which  have  been  laid  down  in  their 
present  positions  by  water  action.  These  clays  are  in  part  a  pure 
white  and  in  part  a  light  yellow  in  color.  Sometimes  the  two  colors 
occur  alternately  in  thin  bands.  The  yellow  clay  is  very  soft  and 
contains  some  silica  in  very. fine  grains.  The  white  clay  is  very  finely 
laminated,  usually  soft,  and  sometimes  breaks  with  a  conchoidal 
fracture.  It  possesses  marked  plastic  properties,  and  for  some  years 
has  been  used  in  pottery  work. 
Sopenah  district. — In  the  valley  of  Cowlitz  River,  especially  about 
and  east  of  Sopenah,  the  existence  of  large  bodies  of  clay  has  been 
known  for  some  time.  The  deposits  which  have  been  worked  thus 
far  all  lie  very  near  Sopenah  and  the  clay  has  been  used  chiefly  by 
the  Little  Falls  Fire  Clay  Company  in  the  manufacture  of  sewer 
pipe,  fire  brick,  common  brick,  and  draintile.  The  clay  beds  form 
part  of  an  extensive  series  of  sedimentary  rocks  of  Eocene  age, 
mainly  clays  and  sandstones.  Within  the  clays  shells  of  marine 
animals  are  commonly  found,  and  in  adjacent  sandstone  beds  such 
shells  occur  in  great  abundance.  Several  pits  have  been  opened  in 
the  clay  beds,  the  necessar}^  stripping  of  soil  amounting  to  about  5 
feet.  For  a  distance  of  about  12  feet  below  the  surface  the  clay  is 
usually  jointed  and  is  of  a  red  or  a  reddish-brown  color.  Below  the 
weathered  zone  the  color  of  the  clay  is  a  light  gray,  sometimes 
approaching  blue.  In  all  the  clay  flakes  of  muscovite  mica  occur, 
and  occasionally  some  sandy  layers  are  encountered.  It  has  been 
found  in  working  the  clay  that  the  weathered  part  is  more  desirable 
than  the  unweathered  part,  since  the  fusion  point  of  the  latter  is 
rather  low.  In  practice  it  has  been  found  also  that  better  sewer  pipe 
can  be  made  by  adding  sand  to  the  clay  than  by  using  the  clay  alone. 
Outcrops  of  clay  deposits  have  been  noted  at  a  number  of  places 
in  the  vicinity  of  Chehalis.  The  clays  are  residual  and  comprise  a 
part  of  the  coal-measure  series  of  the  region.  They  lie  in  thick  beds, 
dip  gently,  and  are  very  easy  of  access.  The  quality  of  the  claj^s  has 
been  but  slightly  investigated.  A  plant  for  the  manufacture  of 
common  brick  has  lately  been  installed  at  Chehalis.  The  clay  used 
is  taken  from  the  surface,  only  a  few  inches  of  soil  and  vegetable 
matter  being  removed.  It  is  light  brown,  and  contains  some  fine 
sand  and  minute  flakes  of  muscovite  mica. 
Whitman  County. — Large  deposits  of  clay  are  found  along  Palouse 
River,  especially  near  the  town  of  Palouse  and  to  the  east  of  it.  The 
clay  occurs  in  distinct  layers  and  is  therefore  of  sedimentary  origin. 
