484    Prof.  Wilson  and  Mr.  Gold:  Electrical  Conductivity  of 
These  results  relate  to  two  gases  only  ;  but  so  far  as  they  go 
they  show  :— (i.)  That  the  range  varies  inversely  as  the  pres- 
sure, which  result  might  have  been  anticipated  ;  (ii.)  that  the 
total  number  of  ions  set  free  in  a  gas  is  independent  of  the 
pressure,  but  is  different  in  different  gases.  The  total  ion- 
ization is  greater  in  ethyl  chloride  than  in  air.  This  is  a 
contrary  result  to  that  which  we  obtained  during  our  experi- 
ments on  absorption.  We  were  unaware  at  that  time  of  the 
enormous  force  required  to  saturate  the  complex  gas. 
Finally,  the  following  experiments  may  be  briefly 
described: — 
We  have  tried  the  effect  of  reversing  the  field  on  the  rela- 
tion between  current  and  potential,  and  found  a  result  which 
was  practically  negative.  We  have  found  a  similar  result 
when  the  a.  particles  were  not  shot  straight  across  the  ion- 
ization chamber  in  the  direction  of  the  lines  of  force,  but  in  a 
slanting  direction.  These  experiments  were  made  in  the 
endeavour  to  find  whether  there  was  any  relation  between  the 
direction  in  which  electrons  were  projected  and  the  direction 
of  the  applied  field.  We  have  also  tried  to  alter  the  range 
in  air  by  using  different  potential  gradients,  with  the  idea 
that  it  might  be  possible  to  obtain  ions  from  an  atom  traversed 
by  a  slower  a.  particle,  if  only  enough  electric  force  were 
applied.  But  the  result  was  the  same,  no  matter  whether  the 
force  was  20  volts  to  the  cm.  or  2000  ;  and  a  variation  of  '2 
mm.  could  hardly  have  escaped  detection. 
During  the  progress  of  this  work,  one  of  us  (R.  D.  Klee- 
man)  left  Australia  for  England.  We  wish  to  acknowledge 
with  gratitude  the  assistance  of  Mr.  H.  J.  Priest,  B.Sc,  in 
completing  the  observations. 
XL II.  On  the  Electrical  Conductivity  of  Flames  containing 
Salt  Vapours  for  Rapidly  Alternating  Currents.  By  H.  A. 
Wilsox,  M.A.,  JJ.Sc,  M.Sc,  Professor  of  Physics,  King's 
College,  London,  Fellow  of  Trinity  College,  Cambridge,  and 
E.  GrOLD,  B.A.,  Hutchinson  Student,  St.  John's  College, 
Cambridge  *. 
THE  following  paper  contains  an  account  of  a  series  of 
experiments  on  the  electrical  conductivity  of  a  Bunsen 
flame  containing  various  alkali  salt  vapours,  the  currents 
used  being  alternating  ones  with  frequencies  varying  from 
7-14  x  104  to  6'2  x  106  per  second. 
The    conductivity   was    measured    between    two  platinum 
electrodes  immersed  in  the  flame,  and  the  variation  of  the 
*  Communicated  by  the  Physical  Society  :  read  November  24,  1905. 
