Recombination  of  Ions  in  Air  and  other  Gases.        473 
3  Turns. 
300  volts 
(Metal  over  Ra). 
300  volts. 
47 
47 
52 
.30 
|  |f  11}  Mean  =49         1 
>Net  leak  = 
99  00  03  }  ^au  =  465  j 
416=1.3  (say). 
10  volts 
(Metal  over  Ra). 
10  volts. 
47 
47 
51 
50 
41  «§}  Mean  =  38         ] 
>Net  leak  = 
26  31  31 1  ,r            o-o 
23  28  27  rMean  =  3'8J 
340  =  I '3. 
300  volts 
(Metal  over  Ra). 
300  volts. 
47 
47 
52 
50 
%%}  Mean  =  48         1 
>Net  leak  = 
06  07  04]  ,r            ..A 
S3  83  83fMean  =  44oJ 
396  =  I,. 
.-.     Mean  value  of  I3  =  406. 
Value  of  I'3  =  340. 
Hence,  I6/I'6  =  1*208,  and  I3/I';>  =  1-193.  A  repetition  of 
the  experiment,  in  different  order,  gave  I6/l3  =  1*947,  and 
I'6/I'3  =  1*897.  These  agree  well  with  each  other,  for  we 
find  from  the  first  set  that  I6F3/r6I3  =  1*013,  and  from  the 
second  that  the  same  fraction  =  1*025. 
The  fraction  I6/1'6  is  the  ratio  of  the  saturation  current  in  a 
chamber  about  6  mm.  wide  to  the  current  when  the  potential 
gradient  is  about  35  volts  per  cm.  ;  and  13/I'3  is  the  ratio 
when  the  chamber  is  3  mm.  wide,  all  other  conditions  being 
exactly  the  same.  It  ought,  perhaps,  to  be  mentioned  that 
the  current  for  the  chamber  of  double  width  was  not  quite 
twice  that  for  the  other,  because  the  widening  was  effected  by 
raising  the  top  plate,  and  so  adding  to  the  chamber  a  layer 
of  air  which  was  about  3  mm.  further  away  from  the  radium 
than  the  original  layer.  As  a  little  heap  of  radium  bromide 
was  used,  the  curve  was  of  the  form  shown  in  Plate  xviii., 
Philosophical  Magazine,  December  1904,  so  that  ionization 
decreased  as  distance  from  the  radium  increased.  These 
results  show  clearly  the  existence  of  at  least  one  effect  which 
we  should  expect  to  find  as  a  result  of  initial  recombination. 
Again,  we  ought  to  find  that  variation  in  current  strength, 
caused  by  altering  the  power  of  the  ionizing  agent,  makes 
little  difference  to  the  form  of  the  curve  when  the  current  is 
small.  We  have  made  several  experiments  in  this  direction 
also.  In  fig.  2,  curves  A  and  B  show  the  results  of  experi- 
ments with  currents  which  were  of  an  order  ten  times  smaller 
Phil.  Mag.  S.  6.  Vol.  11.  No.  64.  April  190G.         2  I 
