ON  SOME  POINTS  OP  CHEMICAL  THEORY,  ETC. 
387 
6,  the  carbon  number,  twelve  times  ;  in  8,  the  oxygen  number, 
sixteen  times  ;  in  14,  the  nitrogen  number,  twenty-eight  times  ; 
and  in  35-5,  the  chlorine  number,  seventy-one  times.  In  this 
way  it  is  shown,  that  the  adoption  of  35*5  as  the  number  for 
chlorine,  is  not  inconsistent  with  the  general  law  of  exact  mul- 
tiples ;  though  it  does  not  permit  of  the  selection  of  unity,  that 
is,  the  equivalent  of  hydrogen,  for  the  common  divisor. 
If  we  suppose  that  the  final  result  of  the  investigation,  now  in 
progress,  shall  be  to  prove  that  the  common  divisor  of  all  the 
equivalents  is  a  number,  equal  to  half  the  equivalent  of  hydro- 
gen, the  question  still  remains  to  be  answered,  what  hypothesis 
shall  we  adopt  to  explain  this  curious  relation  of  the  equivalent 
numbers  ?  The  most  plausible  one  is  that  the  common  divisor 
represents  the  equivalent  of  an  unknown  element,  which  would, 
therefore,  have  an  equivalent  weight,  half  that  of  hydrogen. 
Dumas  throws  out  this  conjecture,  and  broaches  the  hypothesis 
that  all  the  so-called  elements  may  possibly  be  formed  of  one 
kind  of  matter  ;  the  unknown  element  being  the  parent  matter, 
out  of  which  all  the  other  elements  are  formed,  by  its  addition 
to  itself,  condensed  to  a  greater  or  le3s.degree.  This  hypothesis 
of  the  essential  identity  of  all  matter,  appears  to  me  to  be  ex- 
tremely improbable. 
It  is  now  more  than  thirty  years,  since  a  German  mineralogist 
called  my  attention  to  the  fact,  first  observed,  I  believe,  by  the 
German  chemists,  that  several  cases  existed,  where  three  ele- 
ments, having  similar  properties,  formed  a  triad,  and  possessed 
equivalents,  so  peculiarly  related,  that,  if  the  largest  and  smallest 
were  added  together,  and  divided  by  2,  the  quotient  would  be 
the  intermediate  equivalent.  This  curious  relation  of  the  equiva- 
lents of  allied  elements  was  at  first  thought  to  be  fortuitous, 
and  likely  to  disappear  when  the  numbers  were  more  correctly 
determined.  The  progress  of  science,  however,  has  not  realized 
this  surmise  ;  but,  on  the  contrary,  rather  gives  support  to  the 
alleged  relation.  Dumas  has  lecently  taken  up  this  subject, 
and  has  brought  forward  so  many  cases  in  support  of  the  relation, 
that  it  may  be  considered  almost  as  a  law.  Thus  16,  added  to 
64,  the  equivalents  of  sulphur  and  tellurium,  gives  80,  the  half  of 
which,  namely  40,  is  the  equivalent  of  selenium.  Again,  20 
and  68,  the  equivalents  of  calcium  and  barium,  added  together, 
