124 
Life- History  of  a  Doctrine. 
I  Am.  Jour.  Pharm. 
I      March.  1903. 
dx 
dt 
=  gt  -\-  constant, 
however,  made  all  clear.  He  tried  to  convey  his  own  thoughts  to 
his  students  and  he  was  greeted  with  open-mouthed  wonder.  So, 
too,  I  knew  a  physicist  who  approached  his  problems  in  much  the 
same  way.  He  would  not  let  his  class  of  beginners  work  with  a 
lever  and  deduce  the  law  from  the  results  of  their  own  experiments, 
which  to  me  appeared  an  instructive  exercise,  "  for,"  he  said,  "  the 
lever  is  a  mathematical  instrument  and  it  is  not  necessary  to  experi- 
ment with  it  in  order  to  determine  the  laws  of  its  action." 
On  the  other  hand,  I  have  been  told  that  Lord  Kelvin  says  he 
cannot  form  a  clear  conception  of  any  natural  phenomenon  without 
the  aid  of  a  model.  I  remember  years  ago,  when  he  was  lecturing 
at  the  Johns  Hopkins  University,  that  he  showed  his  hearers  a 
beautiful  model  of  light  waves,  and  I  am  sure  they  had  the  power  to 
convey  light  to  a  number  of  brains  that  would  have  been  in  dark- 
ness if  any  other  method  had  been  adopted.  Whether  we  will  or 
not,  we  have  the  non-mathematical  mind  to  deal  with,  and  this 
brings  me  back  to  chemistry  and  that  special  doctrine  of  chemistry 
that  has  to  deal  with  atoms. 
The  doctrine  of  atoms  is  still  alive,  though  it  came  into  being 
about  a  hundred  years  ago.  It  has  been  proved  to  be  illogical,  as 
the  ether  that  fills  all  space  has  been  shown  to  be  incapable  of 
existence.  Properties  must  be  ascribed  to  the  atom  that  it  cannot 
possess  and  the  same  is  true  of  the  ether.  What  are  we  to  do  ? 
Throw  over  the  atom  and  the  ether  ?  Although  both  have  been 
convicted  of  being  illogical,  I  do  not  think  it  would  be  logical  to 
give  them  up,  tor  they  are  helpful  in  spite  of  their  shortcomings,  and 
in  some  way  they  suggest  great  truths.  They  are  symbolic.  It 
would  be  as  illogical  to  give  them  up  as  it  is,  in  my  opinion,  to  deny 
the  existence  of  a  power  in  the  universe  infinitely  greater  than  any 
of  the  manifestations  familiar  to  us  ;  infinitely  greater  than  man ;  a 
power  "  that  passeth  all  understanding."  The  atom  helps  us;  the 
ether  helps  the  physicist.  We  cannot  give  them  up  without  losing 
our  hold  on  many  phenomena.  For  a  century  the  phenomena  of 
chemistry  has  been  interpreted  in  terms  of  atoms.  Take  away  that 
conception  and,  though  it  would  be  possible  to  deal  with  these 
phenomena,  I  cannot  believe  that  they  would  appear  as  clear  as  they 
now  do.    In  an  address  before  the  chemical  section  of  the  British 
