Among  the  points  which  are  beyond  dispute,  it  is,
tinn"'? nSS:  first,  evident,  and  no  chemist  has  ever  doubted  it,  that
cai  Chemistry,  g^iggtances  differ  as  much  in  the  proportion  as  in  the
nature  of  their  constituent  principles.  It  is  an  axiom  of  chemical
philosophy  that  any  change  whatever  in  the  numerical  composition
causes  a  change  in  the  whole  of  the  specific  properties,  in  a  more
marked  degree  as  the  alteration  is  greater.  Varied  and  gradual
above  all  others  as  are  the  proportions  produced  by  the  chemical
phenomena  proper  to  living  bodies,  they  afford  a  striking  confirmar
tion  to  this  universal  maxim.  Therefore,  in  the  lowest  stages  of
chemical  analysis,  chemists  have  always  endeavored  to  assign,  as  a
characteristic  property,  the  proportion  of  the  elements  of  each  sub-
stance, as  far  as  possible :  and  when  this  was  omitted,  it  was  on
the  vmderstanding  that  the  proposed  combisration  admitted  of  only
a  certain  proportion  ;  as  in  the  case  of  the  neutral  salts.
