NOTES  ON  THE  NEW  ALMADEN  QUICKSILVER  MINES.  521 
ore  by  a  wall  pierced  with  numerous  openings  by  the  omission  of 
bricks  for  that  purpose. 
Connected  with  the  furnace  is  a  series  of  lofty  and  capacious 
chambers,  also  of  masonry,  through  which  the  whole  product  of 
combustion  is  compelled  to  pass  alternately  above  and  below, 
from  chamber  to  chamber,  until  all  the  available  mercury  is 
condensed.  The  draft  from  these  furnaces  is  carried  by  in- 
clined stacks  up  to  the  top  of  a  lofty  hill  several  hundred  feet 
distant ;  and  here  the  sulphurous  acid  and  other  effete  products 
of  the  furnace  are  discharged.  Formerly,  no  precautions  were 
taken  to  prevent  the  escape  of  mercury  through  the  founda- 
tions of  the  furnace  to  the  earth  beneath :  now,  the  furnaces 
stand  upon  double  arches  of  brick-work,  and  plates  of  iron  are 
built  into  the  foundations,  so  as  to  cut  off  entirely  all  descend- 
ing particles  of  the  metal  and  turn  them  inward.  To  be  con- 
vinced of  the  importance  of  this  precaution,  it  is  sufficient  to 
watch  the  operation  of  the  furnace  for  a  few  moments,  when  an 
intermittent  stream  may  be  seen  to  flow  into  a  reservoir  pro- 
vided for  it,  and  which  by  the  former  process  was  completely 
lost  in  the  earth. 
On  taking  up  the  foundations  of  some  of  the  old  furnaces, 
within  the  last  two  years,  the  metal  was  found  to  have  pene- 
trated, or  rather  permeated,  completely  through  the  foundation 
and  clay  of  the  substructure  down  to  the  bed-rock  beneath,  a 
depth  of  not  less  than  25  or  30  feet.  Over  2000  flasks  of  mer- 
cury were  thus  recovered  in  a  single  year  from  the  foundations 
of  the  two  furnaces.  This  loss  is  entirely  avoided  by  the  im- 
proved construction  which  has  been  adopted. 
The  whole  process  of  reduction  is  extremely  simple,  the  time 
occupied  from  one  charge  to  another  being  usually  about  seven 
days.  The  metal  begins  to  run  in  from  four  to  six  hours  after 
the  fires  are  lighted,  and  in  about  sixty  hours  the  process  is 
completed.  The  metal  is  conducted  through  various  condensing 
chambers  by  means  of  pipes  of  iron,  to  a  "  crane-neck,"  which 
discharges  into  capacious  kettles.  It  undergoes  no  further 
preparatian  for  market,  being  quite  clean  from  all  dross. 
Deducting  2£  years,  during  which  the  mines  were  in  a  state 
of  inactivity,  pending  the  decision  of  {he  law-suit,  the  average 
monthly  product  for  12j  years  has  been  not  far  from  2,500 
