334         CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1906,   PART    I. 
and  Clay  Company  are  engaged  in  the  manufacture  of  such  brick,  and 
the  Pennsylvania  Tile  Works,  at  Aspers  (Bendersville  station,  on 
Gettysburg  and  Harrisburg  Railroad),  was  reported  by  Hopkins  to  be 
manufacturing  white  encaustic  or  enameled  tile.  The  South  Mountain 
Mining  and  Iron  Company,  of  Pine  Grove  Furnace,  is  manufacturing 
unverified  pressed  brick. 
Other  uses. — As  pointed  out  by  Hopkins,  the  white  clay  possesses 
many  of  the  requirements  of  the  potter's  mixture  for  china  ware. 
Although  it  is  more  siliceous,  higher  in  potash,  and  less  plastic  than 
ball  clay,  which  is  the  clay  used  in  pottery  manufacture,  the  proper 
mixture  apparently  can  be  readily  obtained  by  adding  to  it  correj 
spondingly  less  silica  and  feldspar  than  is  customary,  the  exact 
proportions  to  he  determined  by  chemical  analyses.  The  plasticity 
and  cohesiveness  may  also  need  to  be  increased  by  the  addition  of  a 
small  amount  of  ball  clay,  as  for  brick  manufacl  ure. 
It  is  known  thai  white  day  is  used  as  an  adulterant  in  various 
substances,  especially  in  paint.  Some  of  the  clay  Prom  this  area  may 
be  sold  for  this  purpose.  Hopkins  also  mention.--  that  some  of  it  is 
used  for  calcimining,  for  w  Inch  it  is  well  adapted. 
