Pyfometry  and  dreometry.  Set  . 44  j 
on  the  Barometer,  which  at  that  time  I had  already  de- 
termined. 
The  irregularities  of  this  laft  metallic  Thermometer 
are  of  the  fame  nature,  but  much  more  confiderable  than 
thofe  of  the  other:  this  had  already  made  me  fufpedf, 
that  they  proceeded  from  the  metal  itfelf,  though  the 
wood,  of  which  the  frame  was  made,  appeared  a little 
fufpicious  on  account  of  the  humidity. 
I met  with  the  fame  effects  in  my  laft  experiments, 
when  the  frame  no  longer  interfered;  and  the  irregularity 
fhewed  itfelf  in  this  manner.  Whenever  I had  obferved 
the  point  at  which  my  Microfcope  pointed  upon  the  la- 
mella of  brafs,  which  was  fufpended,  with  the  rod  of 
glafs,  in  water  at  the  temperature  of  the  air,  and 
then  put  warm  water  in  the  room  of  this ; if  I cooled  the 
water 
la  correction  a faire  pour  la  chaleur  fur  le  Barometfe,  que  j*avois  deja  dcter- 
minee  alors. 
Les  irregularites  de  ce  dernier  Thermometre  metallique,  qui  font  de  memo 
nature  que  celles  de  1* autre,  font  encore  beaucoup  plus  grandes;  ce  qui  m’avoit 
deja  fait  foup^onner  qu’elles  procedoient  du  metal  meme;  quoique  la  mqntiire, 
qui  eft  de  bois  dans  les  deux  machines,  me  fut  un  peu  fufpe&e  a caufe  de 
Phumiditl. 
Dans  mes  dernieres  experiences  j’ai  eprouve  les  memes  efFets;  et  ici  la  mon- 
ture  n’etoit  plus  une  raifon  de  doute.  Void  comment  cette  irregularite  fe  ma- 
nifeftoit.  Quand  j*avois  obferve  le  point  ou  mon  vlicrofcope  vifoit  fur  la  lame 
de  Jeton  fufpendue  avec  la  branche  de  verre  dans  l’eau  a la  temperature  de  Pair, 
et  que  je  fubftitilois  a cette  eau  de  l’eau  chaude;  ftje  refroidilfois  l’eau  peu  a peu, 
Vol.  LXVIII.  G g g je 
