PHILOSOPHICAL  TEANSACTIONS. 
I.  The  Bakeeian  Lectuee. — On  the  Stratifications  and  Baric  Band  in  Electrical  Dis- 
charges as  observed  in  Torricellian  Vacua.  By  John  P.  Gassiot,  V.P.B.S. 
Eeceived  Januaiy  6,- — Eead  March  4,  1858. 
1.  The  striated  condition  of  the  electrical  discharge  in  vacuo  that  takes  place  when  the 
terminal  wires  of  Ruhmkoefp’s  inductive  coil  are  inserted  into  a well-exhausted  receiver, 
in  which  a small  piece  of  phosphorus  has  been  previously  placed,  was  first  announced 
by  Mr.  Geove  in  his  communication  to  the  Eoyal  Society,  7th  January,  1852  ; his  paper 
is  printed  in  the  first  part  of  the  Transactions  for  that  year,  and  was  subsequently 
published  in  the  Philosophical  Magazine  of  December  1852,  with  a supplementary  note 
dated  9th  June,  wherein  Mr.  Geove  states  “that  he  had  found  the  transverse  dark 
bands  could  be  produced  in  other  gases  when  much  attenuated,  probably  in  all,  and  that 
he  thought  the  reason  why  they  are  more  easily  seen  in  phosphorus  vapour  is  that  all 
the  oxygen  having  been  consumed,  a better  vacuum  is  formed.” 
2.  I had,  at  the  time,  the  pleasure  of  witnessing  many  of  these  experiments,  which  are 
now  so  well  known  to  electricians ; shortly  afterwards  I examined  the  discharge  in  a 
Torricellian  vacuum : my  apparatus  consisted  of  a glass  cylinder  6 inches  long,  in  which 
two  platinum  wires  are  hermetically  sealed  about  4 inches  apart ; the  cylinder  forms 
the  upper  portion  of  a barometer,  the  lower  part  being  made  of  the  usual  sized  tubing ; 
the  mercury,  when  at  the  height  of  30  inches,  reaches  to  within  about  6 inches  of  the 
cylinder ; the  mercury  was  carefully  boiled  in  the  usual  manner  by  M.  Negeetti,  and 
the  apparatus  fixed  in  my  laboratory,  where  it  at  present  remains  as  originally  placed. 
3.  When  the  discharge  is  made  with  a Ruhmkoeff’s  coil,  by  connecting  the  above 
platinum  wires  with  the  terminals  of  that  apparatus,  the  cylinder  is  brilliantly  illumi- 
nated with  a dense  white  phosphorescent  light,  filling  the  entire  vacuum,  the  intensity 
of  the  light  depending  on  the  energy  of  the  battery.  The  mercury  sinks  at  each  dis- 
charge, but  not  the  slightest  trace  of  any  transverse  bands  can  be  detected. 
4.  The  phenomenon  of  stratifications  in  the  discharge  in  vacuo  were  subsequently 
observed  in  Paris  by  M.  Euhmkoeff,  who  obtained  the  effect  by  using  the  vapour  of 
alcohol ; they  were  again  noticed  by  Masson,  Du  Moncel,  Quet,  and  other  continental 
MDCCCLVIII.  B 
