PROCESS  OF  TAKING  PHOTOGRAPHIC  PICTURES  ON  GLASS.  549 
pose.  By  the  use  of  the  said  process,  the  beauty  and  perma- 
nency of  such  pictures  are  greatly  increased,  and  I  have  on  this 
account  styled  the  process  "  ambrotype,"  from  the  Greek  word 
ambrotos,  immortal. 
The  first  part  of  my  invention  consists  in  the  use  of  alcohol, 
for  the  purpose  of  depriving  the  gun-cotton,  of  which  the  collo- 
dion is  made,  of  its  moisture  after  it  has  been  washed,  to  free  it 
from  the  acids  used  in  its  manufacture. 
It  has  been  found  that  where  gun-cotton  has  been  exposed  to 
the  action  of  the  atmosphere  for  the  purpose  of  drying  it,  the 
sensitiveness  of  the  collodion  prepared  from  it  is  sensibly  dimin- 
ished. By  the  use  of  alcohol  it  may  be  deprived  of  its  moisture 
after  being  washed,  without  exposure  to  the  air,  and  without  the 
consequent  deterioration  of  its  sensitiveness.  This  part  of  my 
process  I  conduct  as  follows : — So  soon  as  the  cotton  has  been 
sufficiently  exposed  to  the  acids  and  has  been  thoroughly  washed, 
it  is  plunged  into  strong  alcohol,  which  effectually  deprives  it  of 
the  water  which  it  contains,  without  exposing  it  to  the  atmos- 
phere for  the  purpose.  From  this  alcohol  it  is  taken  immediately 
to  the  mixture  in  which  it  is  dissolved  for  the  purpose  of  forming 
the  collodion.  This  mixture  consists  of  ten  parts  of  sulphuric 
ether  and  six  of  alcohol,  or  thereabouts.  The  collodion  thus 
formed  is  allowed  to  remain  until  it  has  settled  perfectly  clear, 
which  usually  requires  about  twenty-four  hours.  It  is  then  de- 
canted, and  to  every  pint  is  added  eighty  grains  of  iodide  of 
potassium  dissolved  in  alcohol.  It  is  then  well  shaken,  and  thir- 
ty-two grains  of  refined  gum  camphor  is  added  to  each  pint  of 
the  collodion,  and  after  it  has  again  settled  it  is  fit  for  use.  The 
object  of  the  camphor  is  to  increase  the  vigor  and  distinctiveness 
of  delineation  of  the  positive  pictures,  and  particularly  of  the 
half  tints.  It  also  greatly  increases  the  beauty  of  the  picture, 
by  giving  a  fineness  of  deposit  not  heretofore  attainedf^by  any 
other  means.  The  use  of  the  gum  camphor  in  the  manner  above 
described  forms  the  second  branch  of  my  invention.  The  collo- 
dion is  then  applied  to  the  surface  of  the  glass  in  the  following 
manner  : — 
The  plate  of  glass  being  held  horizontally,  a  portion  of  the 
collodion  is  poured  upon  it,  and  it  is  then  inclined  in  different 
directions,  so  as  to  cause  the  collodion  to  flow  over  its  whole  sur- 
