WHITE    CLAYS    OF    SOUTH    MOUNTAIN,  PENNSYLVANIA.  331 
the  company  opened  up  the  deposits  at  the  old  Medlar  ore  bank,  at 
Upper  Mill,  and  the  Henry  Clay  deposits,  4  miles  above,  on  the  south 
side  of  Mountain  Creek.  The  Medlar  pit  has  since  been  abandoned 
and  the  company  gets  its  supply  solely  from  Henry  Clay,  paying  a 
royalty  of  10  cents  a  ton,  which  makes  the  cost  of  crude  clay  at  the 
mine  about  $1.30  a  ton. 
The  Henry  Clay  mine  is  operated  by  drifts  from  a  shaft  47  feet  deep 
in  the  rear  of  the  old  ore  pit.  The  main  drift  runs  125  feet  southeast- 
ward from  the  shaft,  and  from  its  end  lateral  drifts  parallel  to  the 
mountain  branch  off.  A  large  amount  of  pure  clay  is  exposed  in  these 
drifts  and  is  being  mined  by  side  entries  and  stoping.  In  a  minor 
drift,  100  feet  long,  which  runs  northwestward  from  the  shaft  toward 
the  valley,  the  white  clay  is  mixed  with  yellow  clay  and  iron  ore,  and 
the  purer  portions  have  been  largely  mined  out.  This  part  of  the 
deposit  may  not  be  in  its  original  position,  for  it  may  have  moved 
down  the  slope  and  become  intimately  mixed  with  the  overlying  clay 
and  iron  ore,  but  the  portion  in  the  southeast  drift  is  probably  in  its 
normal  position  beneath  the  iron-bearing  clay.  It  appears  to  lie  flat 
or  to  rise  gently  eastward  and  probably  forms  the  east  side  of  the  syn- 
cline.  The  mine  is  equipped  with  steam  hoist  and  tram  cars.  As  now 
operated  its  capacity  is  ,33  tons  a  day,  all  of  which  is  used  by  the  brick 
plant  at  Mount  Holly  Springs  in  the  crude  dried  form,  none  being 
refined  at  present. 
On  the  opposite  side  of  the  old  ore  pit,  about  150  feet  northeast  of 
the  clay  opening,  a  shaft  had  been  sunk  7 1  feet  in  ore-bearing  clay, 
which  was  being  mined  for  iron  by  the  company,  which  had  installed 
for  this  purpose  a  steam  bucket  hoist,  an  ore  washer,  and  a  gravity 
tramway  to  the  railroad  siding.  About  15  tons  a  day  were  being 
mined. 
The  refinery  at  the  brick  plant  has  a  capacity  of  30  to  40  tons  a  day 
and  is  furnished  with  three  triple  vertical  blungers  with  revolving  ver- 
tical slatted  grates,  long  flotation  troughs,  rotary  fine  wire  screens,  10 
settling  vats,  10  presses,  and  a  12-track  tunnel  drier.  The  siliceous 
waste  extracted  by  the  refinery  process  was  found  to  be  too  short 
grained  to  make  into  bricks;  in  fact  the  crude  clay  itself  needs  a 
binder  of  plastic  clay  to  give  it  body,  and  since  the  production  from 
the  mine  is  no  more  than  sufficient  to  supply  the  brick  plant,  the 
refinery  has  been  shut  down  for  some  time. 
The  Mount  Holly  Company  makes  an  excellent  hard,  semivitreous 
brick,  for  which  there  is  a  ready  market  at  the  price  of  $20  a  thousand. 
The  light  color  of  the  bricks,  cream  to  light  buff,  makes  them  very 
desirable  for  the  fronts  of  buildings,  while  their  hardness  meets  the 
requirement  for  paving. 
The  clay  from  the  mine  at  Henry  Clay  has  the  necessary  ingredients 
to  produce  a  vitrified  brick,  but  has  not  enough  body  to  hold  its  shape 
