468  Mr.  de  luc  on 
the  reafons  why-  I i'ufpect  the  experiments  made  uporv 
air  in  Manometers,  has  obliged  me  to  fufpend  the  expe-- 
riments  I had  undertaken  upon  the  expanfion  of  woods. 
This  method  of  finding  the  relative  expan fibilities  of 
bodies  may  eallly  be  turned  into  a method  of  finding 
their  abfolute  expanfibilities:  for  if  one  knows  with  cer- 
tainty the  expanfibility  of  the  rod  of  glafs  to  which  all 
the  other  bodies  are  compared ; by  means  of  that,  one 
will  come  to  the  knowledge  of  the  abfolute  expanfibility 
of  all  thefe  bodies. 
The  point  then  would  be  to  give  all  pofiible  attention, 
and  ufe  all  the  refources  of  art,  to  the  determining  the 
expanfibility  of  this  rod  of  glafs ; and  this  one  may  hope 
to  arrive  at  by  this  fame  machine,  as  I fhall  fhew  by 
the  following  account  of  my  firft  trial. 
Effay 
de  fufpe&er  les  experiences  faites  fur  Fair  dans  les  Manometres,  m’ont  oblige  de 
fufpendre  cellcs  que  j’avois  entreprifes  fur  Fexpanfion  des  hois. 
Cette  methode  de  trouver  les  expanfibilites  relatives  des  corps,  peut  encore 
ctre  changee  aifement  en  une  methode  de  trouver  leurs  expanfibilites  abfolues. 
Car  fi  Fon  connoit  par  exemple  celle  de  la  branche  de  verre  a laquelle  on  com- 
parera  tous  les  autres  corps,  on  connoitra  par  elle  Pexpanfibilite  abfolue  de  tous 
ces  corps. 
11  ne  s’agiroit  done  que  de  concentrer  fon  attention,  et  toutes  les  resources  de 
Fart,  fur  la  determination  de  Fexpanfibilite  de  cette  branche  de  verre;  a quoi 
Fon  peut  efperer  de  reuffir  avec  cette  meme  machine,  comme  je  vais  le  montrer 
4’apres  un  premier  eifai. 
EJfai 
