GLASS    SAND    OF    MIDDLE    MISSISSIPPI     BASIN.  461 
were  pot  furnaces,  but  of  the  more  recenl  ones  nearly  all  arc  continuous-tank  furnaces.  The 
continuous-tank  system,  while  involving  a  much  greater  initial  expense,  is  estimated  to 
increase  the  output  about  40  per  cent  over  that  of  the  pot  furnace  with  the  same  amounl  of 
fuel  and  labor,  besides  producing  a  more  uniform  quality  of  glass.  At  Cofreyville  fruit  jars 
are  blown  with  compressed  air  by  a  system  of  automatic  blowpipes  and  molds. 
LOCAL   PRODUCTION   AND    METHODS   OF   PREPARATION   OF   SAND. 
Illinois  and  Missouri  together  furnish  at  present  about  300,000  short  tons  annually, 
nearly  40  per  cent  of  the  total  supply  of  glass  sand  in  the  United  States.  Pennsylvania 
produces  about  33  per  cent,  and  therefore  ranks  first  in  quantity  of  this  product,  with  Illi- 
nois second  and  Missouri  third.  According  to  the  latest  complete  statistics  (for  1905) 
the  average  value  of  glass  sand  per  ton  in  Pennsylvania  was  $1.31,  in  Illinois  63  cents,  and 
in  Missouri  60  cents.  This  notable  difference  in  prices  between  Pennsylvania  and  western 
sand  is  accounted  for  in  part  by  the  fact  that  Pennsylvania  sand  is  somewhat  more  expen- 
sive to  produce,  being  made  from  harder  rock.  A  sharper,  even-grained,  and  consequently 
a  slightly  more  desirable  glass  sand  is  the  result.  Pennsylvania,  West  Virginia,  and  Mary- 
land sands,  all  sold  at  a  high  price,  are  consumed  for  the  most  part  within  those  States, 
and  the  importation  of  western  sand  would  be  expensive.  Therefore  prices  are  largely 
controlled  by  the  cost  of  western  sands  plus  freight  charges.  In  the  Mississippi  Valley 
glass  sand  is  produced  principally  from  the  Fox  River  district  in  north-central  Illinois, 
near  Ottawa,  and  from  Missouri  just  west  of  St.  Louis.  These  sands,  besides  supplying 
a  large  local  demand,  are  shipped  to  all  points  within  a  radius  of  500  miles,  and  frequently 
to  a  greater  distance.  Silica  for  other  purposes,  such  as  steel  eastings,  linings  of  racid  con- 
verters, fire  brick,  etc.,  is  regularly  shipped  to  Pacific  coast  points — Portland,  lacoma, 
and  San  Francisco. 
The  preparation  of  glass  sand  has  become  a  highly  specialized  business,  and  in  the  middle 
Mississippi  Valley  15  or  more  thoroughly  equipped  plants  are  at  present  employed.  The 
large  investments  in  sand  properties  and  mills  have  developed  very  active  competition 
between  these  establishments,  and  this  competition  has  resulted  in  great  care  in  the  prep- 
aration of  glass  sand  and  in  a  high-grade  product.  Besides  glass  sand  almost  an  equal 
quantity  of  other  sand  is  produced  at  these  plants  for  various  purposes,  such  as  molding, 
furnace  lining,  stone  sawing,  grinding  plate  glass,  and  glazing  pottery.  Most  of  this  sand 
requires  less  care  in  selection  and  preparation,  yet  it  brings  almost  as  high  a  price  as  glass 
sand  and  therefore  yields  more  profit. 
The  method  of  treatment  of  glass  sand  depends  on  the  character  of  the  deposit  and  on 
its  position.  Some  beds  of  sandstone  are  so  friable  and  pure  that  only  blasting  down  and 
slight  crushing  are  necessary  before  the  sand  is  dried  and  screened.  Many  plants,  how- 
ever, wash  their  sand  in  course  of  preparation,  particularly  those  in  Illinois,  where  hydraul- 
icking  is  employed  to  obtain  sand  from  the  quarries.  Washing  doubtless  removes,  even 
from  high-grade  sand,  considerable  silica  in  such  a  fine  state  as  to  be  detrimental,  as  well 
as  an  appreciable  quantity  of  undesirable  impurity,  mainly  clay,  as  is  indicated  by  the 
following  analysis  of  slime  from  washings  of  sand  at  Ottawa: 
Analysis  of  slime  from  washings  of  Ottawa,  III.,  sand. 
Silica  (Si02) s7-  -' 
Alumina  (AI2O3)  - 7- 50 
Ferric  oxide  ( Fe203) 52 
Calcium  oxide  (CaO) None- 
Magnesium  oxide  (MgO) None. 
Sodium  oxide  (Na20) 1        20 
Potassium  oxide  (K2O) ,.,..,... J 
95.  ^3 
Remainder  mainly  H2O. 
Bull.  285—06 30 
