woolsey]  CLAYS    OF    OHIO    VALLEY    IN    PENNSYLVANIA.  469 
S.  Barnes  &  Co.  state  that  they  at  one  time  mined  a  small  quantity 
of  it  on  the  bank  of  Beaver  River  opposite  their  works,  about  a  mile 
above  Rochester.  The  Clarion  horizon  is  below  river  level  at  this 
point.  No  analysis  of  this  cla}'  is  available,  but  it  has  been  used  with 
good  results  at  Bolivar,  Pa. 
The  thickness  of  the  Clarion  clay  at  three  localities  in  Pennsylvania 
is  here  given : a 
Thickness  of  Clarion  clay  at  localities  in  Pennsylvania. 
Ft.  In. 
Johnstown,  Cambria  County 3  6 
Bens  Run,  Cambria  County 6  0 
Pinkerton  Point,  Somerset  County 6  0 
As  may  be  seen  in  the  section  on  page  467,  the  Clarion  clay  is  about 
50  feet  above  the  Brookville  clay,  and  it  may  therefore  be  more  easity 
mined  than  the  Brookville. 
Lover  Kittanning  clay. — This  is  the  clay  par  excellence  of  this 
region.  It  is  the  source  of  practically  all  of  the  clay  mined  along 
the  Ohio  River  in  Pennsylvania  and  Ohio,  as  well  as  in  West  Virginia, 
where  Prof.  I.  C.  White  says  it  attains  its  maximum  thickness. 
As  the  Lower  Kittanning  clay  lies  considerably  above  the  clays  last 
mentioned,  it  has  accordingly  a  larger  area  of  exposure  above  river 
level.  It  is,  in  short,  to  be  found  throughout  this  region  above  and 
on  both  sides  of  Ohio  and  Beaver  rivers.  Its  elevation  above  low 
water  varies  from  about  180  feet  at  Beaver  Falls  to  zero  at  Freedom, 
just  below  which  town  it  disappears  under  the  river;  and  from  150 
feet  at  State  line  to  50  at  Phillis  Island,  60  at  Industry,  90  at  Van- 
port,  and  100  at  Beaver.  It  is  not,  however,  actually  exposed  through- 
out this  whole  extent,  but  is  covered  by  broad,  flat  gravel  terraces  at 
Rochester,  Beaver,  Monaca,  west  of  Bellows ville,  east  of  Industry, 
Shippingport,  Georgetown,  and  the  terrace  on  the  north  side  of  the 
river  between  the  last  two  towns.  Elsewhere  it  is  exposed  along  the 
more  precipitous  banks  of  the  rivers  and  may  be  readily  exploited. 
Where  covered  by  river  terraces  it  may  be  exposed  by  excavations 
vaiwing  from  a  few  feet  to  50  feet  at  Monaca,  70  feet  at  Georgetown, 
35  feet  at  Bellowsville,  and  45  feet  east  of  Industry.  At  the  other 
places  the  necessary  excavation  is  less  than  25  feet. 
The  Lower  Kittanning  clay  bed  is  also  exposed  within  the  county 
on  tributaries  to  these  rivers.  Of  these  Brady s  Run,  though  not  the 
largest  tributary,  uncovers  the  greatest  extent  of  this  clay  bed;  for 
while  the  clay  is  at  present  being  mined  only  near  Fallston,  the  coal 
above  it  has  been  opened  for  4  miles  along  this  stream.  The  North 
branch  of  Bradys  Run  exposes  this  coal  for  almost  an  equal  distance. 
Bradys  Run  is  a  straight  stream  of  the  low  grade,  open  valley  type, 
aRies,  H.,  Prof.  Paper  U.  S.  Geol.  Survey  No.  11,  1903,  p.  222. 
