434  Mr.  de  luc  on 
This  is  a fketch  of  my  machine,  the  whole  of  which 
confids  in  the  keeping  the  Microfcope  and  the  point  of 
fufpenfion  of  the  rods  free  from  motion  during  the 
obfervation,  and  in  heating  the  rods  with  water.  I will 
now  give  an  account  of  the  experiments  I have  made 
with  it. 
Application  of  the  method  of  finding  the  proportions  between 
the  expanfibilities  of  differ ent  matters  by  heat. — Deter- 
mination of  the  relative  expanfibilities  of  brafs  and 
glafs. 
The  fil'd  experiment  I made  with  this  machine  was 
that  which  I wanted  for  my  Hygrometer.  I took  a 
glafs  tube,  fimilar  to  thofe  which  are  made  ufe  of  for 
common. 
Voila  l’efquifTe  de  cette  machine,  ou  tout  confide  a rendre  le  Microfcope  etle 
point  de  fufpenfion  des  branches  a l’ab it  de  mouvement  pendant  l’obfervation ; 
et  a echauffer  les  branches  par  le  mo  yen  de  beau.  Je  vais  maintenant  rendre 
compte  des  experiences  que  j’ai  faites  par  fon  moyen. 
Application  ds  la  metbode  de  trouver  les  rapports  des  expanfbilites  de  matleres  dif- 
fer ent  es  par  la  chaleur  .—Determination  des  expanfibilites  relatives  du  let  on  et  du 
•verre . 
La  premiere  experience  que  je  fis  avec  cette  machine,  fut  celle  dont  j’avois 
befoin  pour  mon  Hygrometre.  Je  pris  une  branche  de  verre  percee,  femblable  a 
celles  qu’on  employe  aux.  Barometres  coramuns  dont  le  tube  eft  fort  epais:  ces 
tubes- 
