i7o 
A  Piece  of  Pitchblende. 
Am.  Jour.  Pharm. 
April,  1909.  ij 
aluminum  no  thicker  than  I /500  of  an  inch,  and  are  but  very  slightly 
deflected  out  of  their  course  by  a  magnet.  They  are  believed  to 
consist  of  material  particles  of  a  density  about  twice  as  great  as 
that  of  the  hydrogen  atom,  and  to  be  projected  at  a  speed  of  some 
20,000  miles  per  second.  The  beta  rays  travel  with  a  much  greater 
velocity,  and  are  strongly  deflected  by  a  magnetic  field.  They  are 
regarded  as  particles  of  only  1/1000  the  weight  of  the  hydrogen 
atom,  and  charged  with  negative  electricity.  The  gamma  rays  are 
10,000  times  as  penetrating  as  the  alpha  rays  and  are  not  deflected 
by  the  magnetic  or  electric  field.  They  invariably  accompany  the 
beta  rays,  and  appear  to  be  a  wave  motion  set  up  in  the  ether  by 
the  expulsion  of  the  beta  particles.  The  three  types  of  rays  can  thus 
be  separated  and  distinguished  from  one  another  by  means  of  the 
magnetic  field,  as  well  as  by  their  different  penetrating  powers. 
For  our  knowledge  of  these  radiations  we  are  chiefly  indebted  to 
the  work  of  Ernest  Rutherford,  a  native  of  New  Zealand,  and  now 
Professor  of  Physics  in  Victoria  University,  Manchester,  England. 
The  picture  on  the  screen  shows  the  brilliant  investigator  in  his 
laboratory  at  McGill  University  of  Montreal,  where  most  of  this 
work  was  done. 
But  more  remarkable  even  than  these  investigations  are  some 
other  contributions  which  Rutherford  has  made  to  our  knowledge 
of  the  radio-active  substances ;  indeed  his  experimental  discoveries 
and  his  theoretical  reasoning  have  thrown  such  a  flood  of  light  upon 
the  subject  that  it  may  fairly  be  claimed  to  be  one  of  the  most 
assiduously  cultivated  and  most  productive  fields  of  scientific  re- 
search at  the  present  time. 
Perhaps  the  most  striking  discovery  in  radio-activity  next  to  that 
of  radium,  is  the  observation  that  some  of  the  radio-active  substances 
continuously  give  off  gases  which  have  properties  of  the  most  extra- 
ordinary character.  These  gases  differ  from  all  other  gases  with 
which  we  are  acquainted  in  that  they  rapidly  decompose  or  disinte- 
grate, and  in  being  powerfully  radio-active.  This  was  first  noticed 
by  Rutherford  in  the  case  of  thorium,  and  subsequently  it  was  found 
that  radium,  actinium  and,  perhaps,  other  bodies  of  this  class  give 
off  similar  emanations. 
The  several  emanations  differ  from  one  another  in  their  "  periods 
of  life,"  that  from  radium  being  the  slowest  to  decay  and  therefore 
the  one  which  has  been  best  investigated.  "  The  strongest  and 
strangest  thing  in  the  world,"  are  the  words  in  which  Sir  William 
