INDEXED. 
THE 
LONDON,  EDINBURGH,  and  DUBLIN 
PHILOSOPHICAL    MAGAZINE 
AND 
JOURNAL    OF    SCIENCE. 
[SIXTH    SERIES.] 
MAY   1906. 
LVI.  On  the  Ionization  of  Various  Gases  by  the  a  Particles-  of 
Radium.  By  W.  H.  Bragg,  M.A.,  Elder  Professor  of 
Mathematics  and  Physics  in  the  University  of  Adelaide*. 
IN  a  paper  "  On  the  Recombination  of  Ions  in  Air  and  other 
Gases"  (Phil.  Mag.  April  1906,  p.  466),  Mr.  Kleeman 
and  I  have  described  the  preliminary  steps  of  an  enquiry  into 
the  total  ionization  produced  in  different  gases  by  the  a  particle 
of  radium,  and  the  influence  of  physical  conditions  thereon. 
With  the  assistance  of  Mr.  J.  P.  V.  Madsen,  B.Sc,  I  have 
made  many  experiments  in  continuation  of  this  enquiry.  It  is 
necessarily  a  lengthy  one,  and  in  some  respects  difficult,  so 
that  on  many  of  the  points  involved  no  definite  conclusions 
are  yet  within  reach.  On  others,  results  have  been  obtained 
which  are,  I  think,  of  some  interest  and  importance.  In  this 
paper  I  propose  to  describe  the  work  which  has  been  done  ; 
and,  in  addition,  to  make  some  reference  to  (a)  the  magnetic 
deflexion  of  the  ol  particle,  (b)  its  acquirement  of  a  positive 
charge. 
As  described  in  the  paper  referred  to,  the  total  ionization 
of  a  gas  can  be  measured  in  terms  of  the  product  of  the  co- 
ordinates of  a  certain  point  on  the  ionization  curve.  The 
true  measure  is,  of  course,  the  area  between  the  curve  and 
the  axes  of  coordinates.  But  experiment  shows  that  all 
ionization  curves  due  to  radium  in  radioactive  equilibrium 
are  of  the  same  form,  and  differ  from  each  other  only  in  the 
*  Communicated  by  the  Author. 
Phil.  Mag.  S.  6.  Vol.  11.  No.  65^  May  1906.  2  S 
\P  ( 
I 
