ELECTRICAL  DISCHARGES  AS  OBSERVED  IN  TORRICELLIAN  VACUA. 
15 
51.  Since  the  date  of  my  paper  1 have  made  numerous  experiments,  some  of  which 
require  further  verification  before  they  are  published.  I however  avail  myself  of  the 
opportunity  afforded  by  the  Council  having  appointed  me  to  deliver  the  Bakerian 
Lecture,  to  submit  the  following  for  the  consideration  of  the  Royal  Society. 
52.  Fig.  11  represents  the  vacuum  tube  that  I now  generally  use ; the  vacuum  is 
obtained  by  Mr.  Welsh’s  process  (20.) ; the  tube  is  about  38  inches  in  length,  the  wires 
« 5 32  inches  apart ; cc'  are  moveable  coatings  of  tinfoil  2 inches  long  wrapped  round 
the  tube.  Eig.  ll. 
qa,  <>i 
c 
53.  I have  already  stated  that  I oh  tamed  stratifications  by  the  electrical  machine  (21.), 
and  I have  since  ascertained  that  if  a charged  Leyden  jar  is  discharged  through  a 
vacuum  tube  by  means  of  a wet  string,  the  stratifications  are  as  large  and  as  distinct 
as  when  taken  from  the  induction  coil. 
54.  When  the  discharges  from  an  induction  coil  are  made  from  wire  to  wire,  the  stra- 
tifications appear  as  already  described  (22.) ; and  if  the  tube  is  placed  in  a horizontal 
position  mer  the  pole  of  a magnet^  the  stratifications  evince  a tendency  to  rotate  as  a whole 
in  the. direction  of  the  well-known  law  of  magnetic  rotation ; but  when  the  discharge  is 
made  from  coating  to  coating,  or  from  one  wire  to  one  coating,  an  entirely  new  pheno- 
menon arises : the  stratifications  have  no  longer  a tendency  to  rotate  as  a whole,  but  are 
divided.  If  the  tube  is  now  placed  between  the  poles  of  a powerful  electro-magnet,  one 
set  of  stratifications  are  repelled  from,  and  the  other  attracted  towards,  or  within  the 
bent  portion  of  the  magnet ; when  the  tube  is  placed  on  the  north  pole,  the  divided 
stratifications  arrange  themselves  on  each  side  of  the  tube,  changing  their  respective 
positions  when  placed  on  the  south  pole,  but  in  all  cases  each  set  of  stratifications  are 
concave  in  opposite  directions. 
55.  If  a vacuum  tube,  with  or  without  wires  or  coatings,  is  placed  on*  the  induction 
coil  in  action,  or  on  the  prime  conductor  of  an  electrical  machine,  stratifications  are 
discernible,  and  these  can  be  divided  by  the  magnet ; the  tube,  after  recei\ing  discharges 
from  the  electrical  machine,  retains  the  charge  for  a short  time ; and  if  it  is  in  this  state 
laid  on  a table,  hashes  of  light  can  be  observed  for  several  seconds,  but  gradually  getting 
fainter  and  fainter. 
56.  Having  thus  ascertained  that  there  are  two  distinct  forms  of  the  stratified  elec- 
trical discharge,  I propose,  for  the  sake  of  clearness  of  expression,  to  designate  them  as 
the  direct  and  the  induced  discharge.  The  direct  discharge  is  that  which  is  visible  when 
taken  from  two  wires  hermetically  sealed  in  a vacuum  tube;  this  discharge  has  a ten- 
dency to  rotate  as  a whole  round  the  poles  of  a magnet ; the  induced  discharge  is  that 
which  is  visible  in  the  same  vacuum  when  taken  from  two  metallic  coatings  attached  to 
the  outside  of  the  tube,  or  from  one  coating  and  one  wire,  or  from  one  wire ; one  of 
my  tubes  has  only  one  wire  placed  in  its  centre.  The  induced  discharge  is  divisible  by 
