10 
ME.  GASSIOT  ON  THE  STEATIEICATIONS  AND  DA  EE  BAND  IN 
If  the  wires  or  iron  core  are  made  of  well-softened  iron,  although  they  requii-e  some 
time  to  obtain  their  maximum  power,  they  lose  it  instantly ; consequently  the  more 
sudden  the  contact  is  broken,  the  clearer  and  more  intense  will  the  discharge  appear  in 
vacuo. 
34.  I have  already  alluded  to  the  form  of  the  stratifications  as  figured  in  M.  Du  Moxcel’s 
pamphlet  and  other  papers,  as  also  to  that  of  Dr.  Robinsox  (4.) ; in  the  former  they  are 
concave  towards  the  positive  terminal,  gradually  becoming  parallel  towards  the  centre 
and  then  concave  to  the  negative;  in  Dr.  Robinson’s  drawing  they  are  aR  concave 
towards  the  positive ; the  former  is  the  appearance  the  stratifications  exhibit  when  eight 
or  ten  or  more  cells  are  used  to  excite  the  primary,  and  when  by  the  rapidity  of  the 
action  of  contact  breaker  the  discharges  alternate  from  each  wire  and  intermingle  with 
each  other ; Dr.  Robinson  states  he  used  three  and  subsequently  only  one  of  Gkove’s  ; 
hence  the  difference  in  the  representations. 
36.  While  experimenting  with  a battery  of  thirty  or  forty  cells,  I observed  that  the 
positive  terminal,  when  the  discharge  was  taken  in  air,  became  heated  as  soon  as  the 
negative ; the  cause  of  this,  as  well  as  the  difference  in  the  stratifications,  as  figui'ed  by 
M.  Du  Moncel  and  Dr.  Robinson,  is  explained  by  the  preceding  experiments : in  Dr.  Ro- 
binson’s experiments  the  primary  current  was  excited  by  only  three  cells  of  Grove’s 
battery,  which  will  not  produce  any  sign  of  a luminous  discharge  in  vacuo  on  making 
contact ; the  figure  as  depicted  by  that  gentleman  is  the  discharge  on  breaking  contact ; 
and  when  the  vacuum  was  improved  by  allowing  it  to  remain  for  several  days,  exhausting 
the  receiver  four  times,  each  time  filling  it  with  dry  hydrogen,  the  same  figure  was  pro- 
duced by  a single  cell  of  Grove’s  battery.  The  discharge,  as  figured  in  M.  Du  Moncel’s 
work,  has  precisely  the  appearance  which  is  produced  when  a sufiicient  series  of  Grove’s 
batteries  is  used,  which  will  produce  a luminous  discharge  on  making  as  well  as  breaking 
contact. 
36.  Whether  the  discharge  is  taken  in  a tube  of  5 inches  or  one  of  18  inches,  or 
even  of  5 feet  3 inches  (41.)  in  length,  the  full  intensity  of  the  discharge  is  risible  at  a 
single  contact,  exhibiting  from  80  to  100  stratifications,  their  separation  Rom  each  other 
evidently  depending  on  the  density  of  medium  through  which  the  discharge  takes  place, 
or  the  increased  energy  of  the  primary  current. 
The  luminous  arc  of  the  voltaic  battery  carries  with  it  minute  particles  from  the 
terminals,  and  experiment  has  shown  that  an  emanation  of  pai’ticles  takes  place  Rom 
both  wires,  although  more  powerfully  from  the  positive  to  the  negative*;  Avith  the 
inductive  coil  the  emanation  of  particles  only  proceeds  from  the  negative,  not  in  a 
direct  line  to  the  positive,  but  laterally ; if  the  negative  wire  is  inserted  from  the  top  of 
the  tube,  these  emanations  are  deposited  on  the  sides  of  the  glass,  more  dense  at  the 
part  nearest  the  wRe,  but  not  below  the  level  of  the  extreme  end  of  the  negatrie  wRe ; 
at  the  positive  there  is  not  any  sign  of  deposit,  and  the  wire  remains  bright  and  clear. 
37.  If  care  is  taken  so  as  to  make  the  discharge  in  one  direction,  the  negative  wRe 
* De  la  Eive’s  ‘Electricity,’  vol.  ii.  p.  288. 
