AAu£lst  1^8™'}    Romance  of  Chemical  Elements.  577 
especially  the  rays  emitted  from  uranium  salts,  and  this  led  to  the 
discovery  of  polonium  and  radium  by  Professor  and  Madame  Curie 
in  1898.  Then  followed  a  time  of  great  confusion,  for  everywhere 
new  radioactive  substances  were  discovered.  But  the  mystery  was 
increased  when  it  was  found  that  these  bodies  disappear.  For  in- 
stance Madame  Curie  had  separated  with  much  care  and  time  a  little 
sample  of  polonium  and  sealed  it  into  a  small  glass,  and  put  it  aside. 
After  half  a  year,  when  she  wanted  to  use  it  again,  it  was  gone. 
That  is  the  glass  was  there  all  right,  but  the  polonium  had  left. 
Many  experiments  have  been  carried  on,  and  many  ingenious 
devices  have  been  invented  and  as  a  result  of  the  new  phenomena, 
such  as  radioactivity,  cathode  rays,  X-rays,  etc.,  we  have  been  forced 
to  change  our  conception  of  an  atom.  For  practical  purposes  an 
element  still  consists  of  atoms,  but  these  atoms  are  also  built  up 
of  still  smaller  particles,  of  which  the  electrons  and  the  alpha- 
particles  (which  change  into  the  element  helium)  have  already  been 
isolated.  Our  atomic  theory  is  still  in  the  process  of  being  created, 
and  the  reader  is  more  or  less  familiar  with  the  tendencies  of  mod- 
ern physics  (or  is  it  chemistry?). 
We  have  in  this  way  followed  the  history  of  the  elements,  and 
in  Table  VIII  the  reader  will  find  a  chronological  arrangement. 
This  and  the  other  tables  will  serve  as  a  reference,  for  the  space  of 
the  text  permitted  the  writer  to  mention  only  some  and  not  all  of 
the  elements.  A  careful  study  of  these  tables  will  be  helpf.ul  to 
understand  certain  movements  in  the  history  of  chemistry.  For 
instance  how  the  introduction  of  electrolysis  and  the  spectroscope 
resulted  in  the  discovery  of  some  new  elements,  and  how  the  knowl- 
edge of  about  60  elements  assisted  in  the  formulation  of  the  periodic 
system,  for  these  60  elements  were  the  important  nucleus  of  the 
system.  To-day  the  study  of  the  periodic  relationship  among  the 
elements  will  help  us  to  solve  our  present  problem:  the  constitution 
of  the  atom,  for  we  have  now  with  the  noble  gases  a  continuous  line 
of  elements,  while  the  radioactive  elements  indicate  the  end  of  the 
line,  so  that  we  are  entitled  to  believe  our  system  to  be  complete. 
The  romance  of  the  chemical  elements  is  fascinating,  and  while 
I  am  doubtful  if  I  have  made  the  subject  interesting  to  the  reader,  I 
will  be  satisfied  if  I  succeeded  in  pointing  out  how  knowledge  grows, 
and  how,  by  the  labors  of  our  ancestors,  we  are  enabled  to  lift  the 
veil  of  the  mysteries  of  nature  and  apply  the  natural  laws  for  the 
welfare  of  mankind. 
