^PJrin;i8H72RM'}    Soluble  Glass  and  its  Applications.  175 
coating  for  brick  and  stone.  Soluble  glass  was  first  brought  into 
practical  use  by  Prof.  Fuchs,  of  Munich,  in  Bavaria,  in  the  year  1823, 
and  hence  is  frequently  known  as  Fuchs'  soluble  glass.  At  first  it 
was  prepared  by  fusing  ten  parts  of  pearlashes,  fifteen  parts  of  pow- 
dered quartz,  and  one  part  of  charcoal  together,  and  pulverizing  the 
mass,  which  was  then  added  in  small  portions  at  a  time  to  boiling 
water  until  the  whole  was  dissolved.  The  solution  was  then  evapo- 
rated to  a  jelly-like  consistency,  when  it  was  ready  for  market.  More 
recently  it  has  been  found  that  certain  varieties  of  silica  are  soluble 
in  a  boiling  solution  of  caustic  soda ;  and  also  that,  when  the  temper- 
ature of  an  alkaline  solution  is  greatly  increased,  which  may  be  done 
by  boiling  it  in  a  close  vessel  under  great  pressure,  flints  and  other 
hard  varieties  of  silica  dissolve  rapidly.  It  is  in  this  way,  we  be- 
lieve, that  Ransome  prepares  the  soluble  glass  used  in  the  manufac- 
ture of  his  famous  artificial  stone.  It  is  therefore  obvious,  from  a 
consideration  of  these  methods,  that  soluble  glass  is  readily  prepared ; 
and,  as  the  materials  are  comparatively  cheap,  there  is  no  reason  why 
it  should  not  come  into  very  extensive  use,  provided  it  should  prove 
really  valuable  in  the  arts. 
The  first  notable  application  of  soluble  glass  was  to  the  theatre  of 
Munich,  where  it  was  used  for  the  purpose  of  preventing  the  recur- 
rence of  a  fearful  disaster  by  fire.  Before  trusting  to  its  protecting 
qualities,  however,  a  test  was  made  of  its  powers,  and  a  small  building 
coated  with  soluble  glass  was  erected  in  one  of  the  public  squares,  and 
attempts  made  to  fire  it  at  several  points,  by  placing  small  heaps  of 
light  wood  in  contact  with  it  and  setting  these  heaps  on  fire.  Of  course, 
where  the  flames  came  in  contact  with  the  building,  the  wood  of  which 
it  was  made  was  charred,  and  to  a  certain  extent  destroyed.  But  in  no 
case  did  the  building  itself  take  fire  or  burn  ;  and  the  test  was  deemed 
so  satisfactory  that  the  theatre  was  immediately  coated  in  such  a  way 
as  to  be  made  fireproof.  Since  that  time,  it  has  been  applied  in 
many  cases,  and  always  with  success  whenever  the  application  was 
made  with  a  moderate  amount  of  skill.  That  it  might  be  used  ex- 
tensively for  preventing  fires,  and  for  adding  to  the  durability  of  all 
wooden  structures,  is  unquestionable ;  and  therefore  a  few  hints  as 
to  the  best  methods  of  using  it  may  not  be  out  of  place.  These  hints 
we  are  enabled  to  give  more  readily,  since  the  whole  subject  was  care- 
fully investigated  by  the  celebrated  French  chemist  Dumas,  who  has, 
in  his  "Traite'  de  Chimie  applique  aux  Arts,"  detailed  very  fully  the 
