826 
PERMEABILITY  OE  IRON  BY  HYDROGEN. 
lithographic  ink  ;  the  ink  is  removed  by, benzine,  the  surfaces 
first  covered  by  the  design  are  oxidised,  and  the  treatment 
above  described  is  continued.  At  the  end  of  the  operation  the 
raised  portions  of  the  electro  chemical  plate  intended  for  the 
impression  will  be  found  to  correspond  with  the  tracing  of  the 
dcs  gn,  and  the  hollow  portions  with  the  thickenings  raised  about 
the  design  by  the  mercury. 
This  process,  which  is  the  starting-point  and  the  basis  of  M. 
Dulos'  invention,  has  led  him  to  the  discovery  of  some  more 
simple  methods,  which  have  led  to  important  practical  results, 
the  fusible  metal  or  amalgam  of  copper  substituted  for  mercury 
giving  rapid  and  remarkably  perfect  results. — London  Cliem. 
News,  May  21,  1864,  from  Moniteur  tScientifique,  vi.  215. 
PERMEABILITY  OF  IRON  BY  HYDROGEN. 
Our  readers  may  recollect  our  having,  some  months  ago,  men- 
tioned certain  experiments  made  by  MM.  H.  Sainte- Claire  De- 
vil le  and  Troost,  from  which  it  appeared  that,  by  a  kind  of  endos- 
mosis  scarcely  to  be  suspected  in  the  case  of  a  metal,  hydrogen 
would  pass  through  the  pores  of  a  platinum  tube.  Last  wTeek, 
the  Academy  of  Sciences  received  from  them  anew  paper,  in  which 
they  announce  a  similar  property  in  iron.  The  great  difficulty 
was  to  find  a  tube  answering  to  the  various  conditions  required 
for  the  experiment.  The  best  iron  to  be  found  in  the  markets 
might  still  be  open  to  some  objection,  since  in  point  of  fact  it  is 
a  mere  sponge  flattened  by  a  hammer,  like  common  plantinum. 
They  succeeded  at  length,  through  the  kindness  of  a  friend,  in 
obtaining  a  tube  of  cast  steel,  containing  so  little  carbon  that  it 
did  not  admit  of  being  tempered.  It  ^?as  in  reality  rather  iron 
than  steel,,  and  so  soft  that  it  was  drawrn  into  a  tube  without 
heating  or  soldering,  though  its  sides  were  of  a  thickness  of  from 
three  to  four  millimetres.  To  the  ends  of  this  tube,  two  other 
tubes  of  a  much  smaller  diameter  and  of  copper,  were  soldered 
with  silver  ;  the  whole  was  then  introduced  into  an  open  porce- 
lain tube,  which  was  put  into  a  furnace  ;  a  glass  tube,  luted  to 
one  end,  established  a  communication  with  an  apparatus  generat- 
ing hydrogen  completely  deprived  of  atmospheric  air ;  while  at 
