126 
Life- History  of  a  Doctrine. 
/Am.  Jour.  Pharm. 
I      March,  1903. 
actuality  as  an  unaccounted-for  possibility.  But  then  those  who  use 
any  such  mode  of  expressing  the  facts  without  reference  to  the 
theory  never  fail  also  to  adopt  the  doctrine  of  equivalents,  and 
thus,  by  this  double  act,  implicitly  give  in  their  adherence  to  the 
theory." 
While  the  atomic  theory  can  be  used  without  using  atoms,  this 
must  involve  a  great  effort  for  the  average  mind.  Why  should  we 
make  the  effort  ?  If  we  can  get  a  broader  and  deeper  and  clearer 
view  of  chemical  phenomena  by  making  the  effort,  by  all  means  let 
us  make  it.  Can  we  ?  That  is  the  whole  question.  Apparently, 
not  enough  chemists  have  made  the  effort  to  furnish  us  with  the 
necessary  data  upon  which  to  base  a  conclusion.  I  should  like  to 
ask  a  dozen  chemists  to  give  me  each  his  idea  of  the  atom.  The 
results  would  be  interesting.  Some  years  ago  I  sat  next  the  late 
Bishop  Brooks  at  a  dinner  party,  and  I  had  an  extremely  interesting 
conversation  with  him.  I  remember  many  things  he  said  and,  as 
having  some  bearing  on  the  question  I  am  now  dealing  with,  I  quote 
this  remark:  "I  am  sure,"  he  said,  "  that  every  individual  has  a 
different  conception  of  God.  If  we  could  get  at  these  conceptions 
we  should  probably  be  greatly  surprised  to  find  how  markedly  they 
differ  from  one  another."  Each  individual  injects  his  own  person- 
ality into  his  conceptions,  and  the  conceptions  change  according  to 
circumstances. 
At  first,  weight,  or,  more  accurately,  mass,  was  the  only  attribute 
of  the  atom  that  needed  to  be  taken  into  consideration,  except,  of 
course,  that  power  of  combining  with  other  atoms  which  is  its 
fundamental  attribute.  Soon  after  the  atom  came  to  be  a  part  of 
the  chemist's  equipment  two  important  attempts  were  made  to  add 
electrical  charges  to  the  atoms.  Davy  and  Berzelius  took  different 
views  of  the  way  in  which  the  electrical  charges  led  to  chemical  acts, 
but  they  both  agreed  that  chemical  acts  are  essentially  electrical. 
Every  atom  had  not  only  weight,  but  an  electric  charge  which  did 
not  add  to  its  weight,  but  helped  to  explain  its  activity.  The  atom 
bore  this  charge  for  many  years.  It  was  thought  that  it  gave  it  up 
and  returned  to  its  original  simple  form  when  the  dualistic  concep- 
tion ol  the  constitution  of  compounds  gave  way  to  the  unitary  con- 
ception. When  it  was  found  that  chlorine,  an  electro-negative  ele- 
ment, could  take  the  place  of  the  electro-positive  hydrogen  without 
creating  any  marked  disturbance,  chemists  thought  it  best  to  turn 
