Number  of  Corpuscles  in  an  Atom.  779 
persion  of  the  gas  will  depend  more  on  the  charges  of  the 
atoms  in  a  diatomic  gas  than  on  the  corpuscles  inside  the 
individual  atoms. 
The  theory  o£  the  second  method  is  given  in  my  '  Con- 
duction of  Electricity  through  Gases.'  We  proceed  to  the 
consideration  of  the  third  method,  which  depends  on  the 
absorption  by  matter  of  rapidly  moving  corpuscles. 
If  we  suppose  that  an  atom  consists  of  a  number  of 
corpuscles  distributed  through  positive  electrification,  we 
can  find  an  expression  for  the  absorption  experienced  by  the 
corpuscles  when  they  pass  through  a  collection  of  a  large 
number  of  such  atoms.  The  rapidly  moving  corpuscle  will 
penetrate  the  atom,  and  will  be  deflected  when  it  comes  near 
an  inter-atomic  corpuscle  by  the  repulsion  between  the  cor- 
puscles. This  deflexion  will  produce  an  absorption  of  the 
cathode  particles.  If  the  corpuscle  in  the  atom  is  held  fixed 
by  the  forces  acting  upon  it,  the  colliding  corpuscle  will, 
after  the  collision,  have  the  same  velocity  as  before,  though 
the  direction  of  its  motion  will  be  deflected.  If  the  inter- 
atomic corpuscle  A  is  not  fixed,  the  colliding  corpuscle  B 
will  communicate  some  energy  to  it  and  will  itself  go  off 
with  diminished  energy.  Without  solving  the  very  com- 
plicated problem  which  presents  itself  when  we  take  into 
account  the  forces  exerted  on  A  by  the  other  corpuscles,  we 
can  form  some  idea  of  the  effects  produced  by  the  constraint 
introduced  by  such  forces  by  following  the  effects  produced 
by  increasing  the  mass  of  A.  The  general  effect  of  great 
constraint  would  be  represented  by  supposing  the  mass  of  A 
to  be  very  large,  while  absence  of  constraint  would  be 
represented  by  supposing  the  mass  of  A  to  be  equal  to  that 
of  B. 
Let  M1?  M2  be  the  masses  of  the  corpuscles  A  and  B 
respectively.  We  shall  suppose  that  the  velocity  of  the 
colliding  corpuscle  is  so  great  that  in  comparison  the  cor- 
puscles in  the  atom  may  be  regarded  as  at  rest.  Let  V  be 
the  velocity  of  A  before  the  collision,  b  the  perpendicular  let 
fall  from  A  on  V.  If  20  is  the  anode  throuoh  which  the 
direction  of  relative  motion  is  deflected  by  the  collision,  we 
can  easily  show  that 
sin2  6  = 
/>2V4/   M^Mg   Y 
+   e4    \MJ  +  M2/ 
the  force  between  two  corpuscles  separated  by  a  distance  r 
being   assumed   equal   to  e^fr*.      Hence,    if   u,   u'    are    the 
3E2 
