226       Recent  Literature  Relating  to  Pharmacy.  {AmMay^903frm' 
that  they  ionize  gases  and  make  them  conductors  of  electricity. 
They  also  induce  phosphorescence  in  phosphorescent  bodies.  These 
emanations  have  been  called  Becquerel  rays,  from  their  discoverer, 
Monsieur  Henri  Becquerel. 
These  Becquerel  rays  appear  to  be  of  a  composite  nature,  no  less 
than  three  distinct  rays  or  forms  of  energy  being  recognized  at  the 
present  time  as  emanating  from  the  so-called  radioactive  materials. 
A-rays  are  said  to  be  readily  absorbed  by  opaque,  or  even  trans- 
parent bodies;  they  are  not  deflected  in  a  magnetic  field,  and  act  as 
ionizing  agents. 
B-rays  readily  penetrate  opaque  substances;  they  are  not  as  active 
as  ionizing  agents,  however,  and  in  addition  to  this  are  readily 
deflected  by  a  magnet.  In  this  latter  quality  they  appear  to  resem- 
ble the  cathode  rays. 
In  addition  to  these  two  distinct  forms  of  energy,  radium  also 
emits  luminous  rays;  the  exact  nature  of  this  light  has  not  been 
definitely  determined,  but  it  is  probably  due  to  a  fluorescence  or 
phosphorescence  of  the  material  itself,  caused  by  the  inherent  energy. 
The  Becquerel  rays  are  also  classed  according  to  their  source  or 
origin;  thus  they  are  usually  spoken  of  as  uranium  rays,  radium  rays, 
or  thorium  rays,  according  as  they  are  generated  from  one  or  the 
other. 
Uranium  Rays. — As  noted  above,  uranium  was  the  first  of  the 
known  elements  that  was  found  to  possess  radioactive  properties. 
Becquerel  found  that  the  metal  as  well  as  all  of  the  salts  of  uranium 
were  more  or  less  radioactive.  So  far  as  known  there  is  no  marked 
difference  in  the  activity  of  the  uranium  salts  coming  from  different 
sources.  This  latter  fact  would  appear  to  indicate  that  the  radiations 
were  inherent  in  the  uranium  atom.  This  has  been  questioned,  how- 
ever, and  it  has  been  shown  by  Crookes,  and  later  by  Rutherford 
and  Soddy,  that  by  repeatedly  washing  a  uranium  salt  with  ether  the 
A-rays  are  retained  by  the  insoluble,  while  the  B-rays  are  found  in 
the  ether-soluble  portions.  If  in  addition  to  this  we  remember  that 
several  substances  have  been  isolated  that  are  many  thousand  times 
as  radioactive  as  uranium,  it  will  be  seen  that  the  admixture  of  even 
a  very  minute  portion  of  some  new  and  hitherto  unrecognized  ele- 
mentary body  may  be  the  cause  of  this  radioactive  property. 
Radioactive  Bismuth. — The  observation  that  some  of  the  minerals 
containing  uranium  were  more  highly  radioactive  than  any  of  the 
