120 
Life- History  of  a  Doct?'ine. 
f  Am.  .lour.  Pliarm. 
I      March,  1903. 
which  has  led  me  to  discover  weight  in  all  the  elements,  and  it  is 
reason  which  now  leads  me  to  give  a  flat  denial  to  that  erroneous 
maxim  which  has  been  current  since  the  birth  of  philosopy — that 
the  elements  mutually  undergoing  change,  one  into  the  other,  lose 
or  gain  weight,  according  as  in  changing  they  become  rarefied  or 
condensed.  With  the  arms  of  reason  I  boldly  enter  the  lists  to 
combat  this  error,  and  to  sustain  that  weight  is  so  closely  united  to 
the  primary  matter  of  the  elements  that  they  can  never  be  deprived 
of  it.  The  weight  with  which  each  portion  of  matter  was  endued 
at  the  cradle  will  be  carried  by  it  to  the  grave.  In  whatever  place, 
in  whatever  form,  to  whatever  volume  it  may  be  reduced,  the  same 
weight  always  persists.  But  not  presuming  that  my  statements  are 
on  a  parity  with  those  of  Pythagoras,  so  that  it  suffices  to  have 
advanced  them,  I  support  them  with  a  demonstration  which,  as  I 
conceive,  all  men  of  sense  will  accept.  Let  there  be  taken  a  portion 
of  earth  which  shall  have  in  it  the  smallest  possible  weight,  beyond 
which  no  weight  can  subsist ;  let  this  earth  be  converted  into  water 
by  the  means  known  and  practised  by  nature :  it  is  evident  that  this 
water  will  have  weight,  since  all  water  must  have  it  and  this  weight 
will  either  be  greater  than  that  of  the  earth,  or  less  than  it,  or  else 
equal  to  it.  My  opponents  will  not  say  that  it  is  greater,  for  they 
profess  the  contrary,  and  I  also  am  of  their  opinion :  smaller  it  can- 
not be,  since  we  took  the  smallest  weight  that  can  exist :  there 
remains  then  only  the  case  that  the  two  are  equal,  which  I  under- 
took to  prove.  What  is  shown  of  this  particle  may  be  shown  of 
two,  three,  or  of  a  very  great  number — in  short,  of  all  the  element, 
which  is  composed  of  nothing  else.  The  same  proof  may  be 
extended  to  the  conversion  of  water  into  air,  of  air  into  fire ;  and, 
conversely,  of  the  last  of  these  into  the  first." 
The  idea  that  a  thing  can  be  weighed  by  reason  is,  I  suppose,  an 
inheritance  from  the  old  philosophers  who  seem  to  have  believed 
that  all  the  problems  of  the  universe  could  be  solved  by  mental 
operations,  or  that  any  problem  that  could  not  be  solved  in  that 
way  was  not  worthy  of  their  consideration.  The  first  great  generali- 
zation that  was  reached  after  the  method  of  weighing  was  generally 
adopted  by  chemists  was  what  we  sometimes  call  the  law  of  the 
indestructibility  of  matter,  or,  in  more  refined  language,  the  law  of 
the  conservation  of  mass.  Then  followed  the  laws  of  definite  and 
multiple  proportions.  Now,  a  law  of  nature  is  quite  a  different  thing 
