of  the  recent  Attack  on  the  Atomic  Theory"  513 
sentations  of  these  views  as  necessarily  involving  the  notion  of 
indivisible  portions  of  matter.  True,  the  word  "  atom  n  may  be 
employed,  but  not  in  the  Daltonian  sense  of  the  term,  any  more 
than  it  is  employed  in  that  sense  by  Dr.  Williamson.  Kekule's 
propositions  in  fact  amount  to  these  :  a  large  number  of  organic 
bodies  are  found  to  undergo  changes  and  produce  reactions  which 
are  expressible  by  the  generalization  and  convention  that  the 
formulae  of  these  substances  are  all  capable  of  expression  by  the 
general  dissection 
CU'— CV 
//     \ 
CZ'       cw 
CY'=CX' 
where  U',  V,  W,  Xf,  Y',  Z'  represent  either  H  or  some  other  uni- 
valent radical  respectively.  The  extensions  of  knowledge  brought 
about  since,  and  in  consequence  of,  the  propagation  of  his  views 
are  apparently  referable  much  more  to  the  employment  of  sym- 
bols to  indicate  briefly  and  comprehensively  a  host  of  facts  (or, 
what  is  much  the  same  thing  in  principle,  to  the  use  of  compre- 
hensive terms  such  as  n  atom  "  in  senses  not  involving  any  hypo~ 
thesis,  but  having  only  reference  to  generalizations  and  conventions) , 
than  to  the  influence  of  Dalton's  modification  of  Epicurus's  hy- 
pothesis as  to  the  constitution  of  matter. 
If,  however,  the  term  atomic  theory  be  not  used  in  this  defined 
sense,  but  be  employed,  as  by  Dr.  Williamson,  to  indicate  che- 
mical philosophy  generally,  with  the  exclusion  of  Dalton's  fun- 
damental notion  as  to  the  existence  of  indivisible  portions  of 
matter,  then  the  statement  that  the  advances  in  chemistry  are 
due  to  the  atomic  theory  is  a  virtual  admission  of  my  points,  viz. 
that  the  advantages  arising  from  the  hypothesis  of  Dalton  (as 
opposed  to  his  generalization  and  convention)  are  much  overrated, 
and  that  the  discussion  of  hypotheses  in  connexion  with  pheno- 
mena is  of  comparatively  little  benefit  to  the  chemist  until  he 
can  arrive  at  some  one  hypothesis  sufficiently  comprehensive  to 
take  in  all  the  phenomena  observed  by  him.  Now  it  may  be 
possible  for  the  atomic  hypothesis,  with  the  aid  of  vast  numbers 
of  subsidiary  postulates  and  hypotheses,  to  explain  all  existing 
facts,  more  especially  those  concerning  the  relations  between 
energy  and  chemical  action ;  but  alone  it  certainly  cannot  do  so, 
and  as  yet  it  has  not  been  shown  to  explain  (even  with  such  ad- 
ditions) the  few  isolated  facts  in  this  latter  field  at  present  known 
to  us. 
The  examination  of  this  field  constitutes  the  chemistry  of  the 
future.     As  yet,  however,  this  is  barely  regarded  as  even  form- 
Phil.  Mag.  S.  4.  No.  289.  SuppL  Vol.  43.  2  L 
