ON"  HYDRAULIC  LIMES,  ETC. 
523 
lime  with  an  alkaline  silicate,  both  finely  powdered,  in  the  pro- 
portion of  10  or  12  parts  of  the  latter  to  100  of  the  former,  a 
lime  is  obtained  presenting  all  the  properties  of  an  hydraulic 
lime.  If  the  materials  were  not  well  pulverized,  the  reaction 
would  be  incompleto,  and  an  effect  subsequent  to  the  solidifica- 
tion would  soon  cause  a  disintegration.  Thus  an  hydraulic  lime 
of  which  the  strength  may  be  varied  at  will,  may  be  immediately 
prepared  with  lime  and  a  silicate  ;  and  this  will  allow  of  the 
economical  formation  of  hydraulic  constructions  in  places  where 
there  is  no  hydraulic  lime. 
Silicatization  ;  Artificial  Stones  From  this  the  author  was 
led  to  examine  the  action  of  the  alkaline  silicates  upon  calca- 
reous stones ;  and  the  result  of  his  experiments  leads  him  to  ex- 
pect that  in  this  direction  the  alkaline  silicates  may  be  exten- 
sively applied  to  purposes  of  utility.  By  suspending  powdered 
chalk  in  a  solution  of  silicate  of  potash,  a  cement  is  obtained 
which  hardens  slowly  in  the  air,  acquiring  sufficient  hardness  to 
be  capable  of  application  under  certain  circumstances  in  the  res- 
toration of  monuments,  the  manufacture  of  mouldings,  &c. 
Chalk,  either  in  the  natural  state  or  in  the  form  of  an  artifi- 
cial paste,  when  immersed  in  a  solution  of  silicate  of  potash,  ab- 
sorbs a  certain  quantity  of  silica  even  in  the  cold ;  and  this  may 
become  considerable  by  exposing  the  stone  several  times  alter- 
nately to  the  action  of  the  siliceous  solution  and  to  the  air.  The 
chalk  acquires  a  smooth  appearance,  a  close  grain,  and  a  color 
more  or  less  yellowish,  according  as  it  is  more  or  less  ferrugi- 
nous. Stone  thus  prepared  is  susceptible  of  a  fine  polish  ;  and 
the  hardening,  which  at  first  is  superficial,  penetrates  by  de- 
grees to  the  centre,  even  when  the  stone  is  of  considerable  thick- 
ness. The  process  may  be  employed  in  formation  even  of  very 
delicate  sculptured  ornaments,  for  when  the  chalk  is  very  dry, 
which  is  essential  for  the  production  of  good  results,  the  surface 
undergoes  no  alteration  during  silicatization.  Thus  ornaments 
of  great  hardness  and  unalterable  by  moisture  n  ay  be  obtained 
at  very  small  cost,  and  merely  washing  ancient  monuments 
formed  of  soft  limestones  with  a  solution  of  silicate  of  potash, 
will  preserve  them  from  further  decay  ;  the  same  process  may 
have  a  still  more  general  application  in  countries,  like  Cham- 
pagne, where  chalk  is  almost  the  only  building  material.  Since 
