432  On  the  recent  attack  upon  the  Atomic  Theory. 
of  symbols  and  suffixes  ?  He  repeats  his  definition  of  a  radical 
when  he  describes  what  he  means  by  valency,  which  term,  he 
says,  "  is  applied  to  the  radical  to  indicate  the  quotient  obtained 
by  dividing  the  combining  number  of  the  radical  by  its  equivalent 
in  the  particular  reaction  in  question,"  implying  by  this  that 
valency  is  a  function  of  an  assemblage  of  symbols  ! 
The  author  quotes  Wurtz's  definition  of  an  atom  and  a  mole- 
cule to  show  that  there  are  two  senses  in  which  the  term  "  atom  " 
may  be  employed.  He  says  that  "  in  one  sense  the  atom  is  a 
finite  portion  of  matter  of  given  weight,  and  hence  possessed  of 
dimensions  in  space,  mass,  and  time,"  whatever  the  latter  part 
of  the  sentence  may  mean.  In  the  other  sense  he  describes  the 
atom  to  be  "  a  pure  number  possessed  of  no  dimensions  in  space, 
mass,  and  time."  It  would  probably  astonish  Dr.  Williamson 
to  learn  that  he  looked  upon  an  atom  as  a  pure  number.  Ma- 
thematicians have  not  yet  discovered  that  it  is  a  property  of 
pure  numbers  to  combine  in  definite  proportions. 
Dr.  Wright  says  that  the  generalization  of  multiple  propor- 
tions "  is  not  identical  with  the  hypothesis  of  the  existence  of 
material  atoms,  advanced  to  account  for  the  facts  summed  up  in 
the  generalization  ;  and  to  say  that  the  law  has  no  existence 
apart  from  the  atomic  hypothesis  is  to  give  a  meaning  to  the 
term  atom  different  from  that  attributed  to  it  by  Dalton."  It 
has  been  shown  above  that  the  law  of  multiple  proportions  is 
not  an  experimental  fact ;  it  is  only  assumed  when  the  discre- 
pancy between  the  theoretical  and  observed  numbers  is  accounted 
for  by  the  use  of  the  atomic  theory. 
Thus  it  follows  that  the  method  of  finding  the  formula  of  a 
body  from  its  percentage  composition,  being  a  deduction  from 
Dalton's  law,  is  also  based  upon  the  notion  of  the  existence  of 
atoms.  Dr.  Wright's  analysis  of  the  hydrobromate  of  bromo- 
codeine  would  lead  him  to  the  formula 
C^H^Br^NO, 
containing  fractions  of  atomic  weights,  instead  of  the  formula 
he  adopts, 
C18H21Br2N02; 
but  instead  of  accepting  the  numbers  obtained  by  experiment, 
he  rejects  them,  and  takes  the  nearest  numbers  which  yield  a 
formula  containing  only  integral  multiples  of  atomic  weights. 
This  shows  that  when  an  opportunity  is  offered  to  him  of  choos- 
ing between  the  atomic  theory  and  its  antithesis,  whatever  that 
may  be,  he  accepts  the  atomic  explanation. 
Dr.  Wright  does  not  touch  the  subject  of  direct  and  indirect 
combination,  although  this  affords  one  of  the  strongest  qualitative 
proofs  of  the  existence  of  atoms.  No  compound  is  known  of  which 
