ME.  G.  GOEE  ON  THE  PEOPEETIES  OP  ELECTEO-DEPOSITED  ANTIMONY.  189 
occasion  Avith  a feeble  battery,  when  the  external  air  was  at  66°  Fahr.,  the  coldest  part 
of  the  liquid,  viz.  behind  the  anode,  was  at  67°‘6  Fahr.,  and  the  warmest  part  in  front 
of  the  anode  71°  Fahr.  And  on  another  occasion,  with  a stronger  battery,  consisting  of 
twenty-four  pairs  of  zinc  and  silver  plates,  weakly  excited,  with  an  anode  of  moderate 
size,  a thermometer  in  contact  with  the  front  of  the  anode  rose  from  74°-5  to  87°'5  Fahr. 
16.  Faint  crackling  sounds,  audible  at  about  4 or  5 feet  distant,  frequently  occurred 
in  the  depositing  liquid  during  the  process ; they  issued  from  the  receiving  surface,  and 
appeared  to  be  due  to  alterations  in  the  cohesive  state  of  the  metal,  being  generally 
attended  by  the  production  of  cracks,  and  occasionally  of  complete  rents  in  the  metal ; 
they  most  frequently  occurred  when  the  temperature  of  the  deposit  was  changed  by 
removal  from  the  liquid  or  by  reimmersion.  In  one  instance  metallic  sounds  were 
definitely  traced  to  bubbles  of  gas  suddenly  expelled  with  force  from  a small  spot  of  a 
very  firm  deposit  formed  upon  a bar-magnet  in  the  tartaric  acid  liquid,  but  no  fissure  or 
orifice  was  observable  at  the  part;  they  were  unattended  by  evolution  of  light. 
17.  In  common  with  electro-deposits  generally,  the  inner  and  outer  surfaces  of  these 
deposits  are  in  unequal  states  of  cohesive  tension,  frequently  in  so  great  a degree  as  to 
rend  the  metal  extensively  and  raise  it  from  the  receiving  surface  during  the  process 
in  the  form  of  a curved  sheet  with  its  concave  side  towards  the  anode.  This  separation 
is  very  apt  to  occur  in  depositing  upon  extended  fiat  surfaces,  and  does  not  often  occur 
when  the  form  of  the  surface  is  unfavourable,  as  with  wires,  rods,  bars,  &c.,  where  the 
deposit  extends  around  the  mass,  or  Avhere  it  passes  round  projections,  edges,  &c.,  and 
retains  a hold  thereby.  This  state  of  tension  is  most  manifest  in  thin  deposits,  and 
especially  in  the  first-formed  layer ; for  by  depositing  a thin  layer  of  amorphous  anti- 
mony upon  gold-leaf  attached  by  varnish  to  a tube  of  glass,  the  film  of  gold  was  quickly 
raised  from  the  surface,  and  curled  into  fantastic  shapes  by  the  cohesive  action.  Both 
varieties  of  the  metal  exhibit  this  phenomenon. 
18.  The  fracture  of  amorphous  antimony  is  conchoidal,  smooth,  and  wavy;  that  of 
the  grey  variety  is  crystalline,  radiating  like  hematite.  The  texture  of  the  former  is 
rather  soft  and  weak,  that  of  the  latter  is  quite  hard  and  strong.  The  amorphous  metal 
files  easily,  the  grey  Avith  more  difficulty.  The  grey  metal,  if  struck  by  a hard  substance, 
emits  a clear  metallic  sound,  Avhilst  the  dark  variety  gives  a more  dull  tone.  The 
crystallization  lines  of  grey  antimony  are  at  right  angles  to  the  receiving  surface ; and 
in  several  experiments  of  depositing  upon  magnets,  the  direction  of  those  lines  did  not 
seem  to  be  altered  by  the  magnetism. 
19.  The  amorphous  variety,  if  gently  struck  by  a hard  substance,  undergoes  a rapid 
and  intense  change  throughout  its  mass,  attended  by  development  of  considerable  heat  ; 
the  crystalline  kind  undergoes  no  such  change,  apparently  under  any  circumstances. 
The  change  appears  to  be  molecular  in  its  character;  and  according  to  this  view  the 
crystalline  variety  of  metal  must  be  regarded  as  being  in  a state  of  comparatively  stable 
molecular  equilibrium. 
20.  The  folloAving  are  a few  selected  instances  of  this  phenomenon.  Antimony  aaus 
