464  COPPER  TUBES  MADE  BY  GALVANIC  PROCESS. 
are  produced  over  the  entire  surface  of  the  earth,  especially  over 
uncultivated  tracts,  and  are  the  means  provided  by  nature  to 
disolve  the  mineral  food  of  plants ;  they  are  also  amongst  the 
chief  causes  of  the  exhaustion  of  soils.  In  the  green  sandstone 
strata  of  Surrey,  England,  known  as  "  firestone,"  the  rock  is  light 
and  porous,  and  contains  silica  in  a  soluble  state.  Common 
sandstone  quartz  or  rock  crystal  is  not  acted  upon  by  potash  or 
soda  at  ordinary  temperature,  but  30  per  cent,  and  sometimes 
70  per  cent,  of  the  silica  in  "  fire  stone"  may  be  dissolved.  In 
all  such  cases  the  silica  must  have  been  originally  a  state  of 
chemical  combination  with  lime,  alumina,  or  something  else, 
which  has  been  subsequently  removed.  The  silica  in  the  rotten 
stone  was  soluble,  but  black  marble,  in  a  bedded  state,  never 
was  found  converted  into  rotten- stone — Chemical  News,  London* 
July  30,  1860.  • 
COPPER  TUBES  MADE  BY  GALVANIC  PROCESS. 
Le  G£nie  Industriel,  publishes  the  details  of  a  process  for 
making  copper  tubes  without  soldering,  which  consists  simply  in 
depositing  copper  upon  lead  patterns  by  the  galvanic  battery,  and 
then  melting  out  the  lead.  It  is  said  to  work  perfectly,  and  of 
course  tubes  could  be  made  of  any  desired  form — straight,  curv- 
ed, or  right-angled.  This  suggests  the  idea  of  forming  tubes  in 
the  same  manner  with  cores  of  wax  or  clay.  The  clay  may  be 
forced  into  the  size  of  the  pipe  through  a  draw  plate,  then  al- 
lowed to  harden  slightly,  when  it  may  be  covered  with  plumbago 
and  an  electro  deposit  of  copper  made  upon  it  with  a  galvanic 
battery.  When  the  copper  is  deposited  in  sufficient  thickness 
the  clay  may  be  removed  from  the  interior  by  boiling  the  pipe 
in  water.  To  conduct  this  manufacture  it  would  require  long 
depositing  troughs,  and  the  expense  would  probably  be  too  great 
for  making  strait  copper  tubes ;  but  for  curved  tubes,  such  as 
the  worms  of  stills,  it  would  perhaps  pay.  Curved  copper  tubes 
are  commonly  made  by  filling  strait  tubes  with  hot  resin,  then 
twisting  the  entire  tube  into  its  curved  form.  When  the  resin 
becomes  cool,  it  is  driven  out  by  striking  the  pipe,  which  breaks 
the  resin  core  into  small  pieces. — Ohem.  News,  London,  May 
12th,  1860. 
