Pyrometry  and  Areometry , See. 
in  which  the  difference  of  the  progreffions  between  thefe 
two  liquids  in  their  dilatations  by  heat  was  not  obferved. 
Mr.  de  Reaumur’s  Thermometer,  one  of  the  firft  to 
which  one  endeavoured  toaffign  fixed  points,  was  too  dif- 
ficult in  its  conftrudtion  for  each  Thermometer  to  be 
immediately  graduated;  and  indeed  the  author  himfelf 
only  ufed  his  method  in  making  ftandards  to  which  the 
Thermometers  intended  for  common  ufes  were  after- 
wards compared.  Abbe  nollet,  his  difciple,  who  for 
a long  time  gave  the  ton  for  Thermometers  in  France 
and  in  the  Southern  countries,  followed  his  mafter’s 
method.  The  only  immediate  point  he  marked  upon 
his  Thermometers  was  that  of  freezings  and  he  com- 
pared them  afterwards  in  water  of  30°  of  that  fcale  in 
which  the  real  interval  between  the  freezing  and  boiling 
points  ought  to  be  divided  into  about  ioo°.  By  this  me- 
thod, 
mercure  et  d’efprit  de  vin  ou  1’on  ne  remarquoit  pas  les  differences  de  marche  de 
ces  deux  liquides.  Le  Thermometre  de  Mr  dereaumur,  Pun  des  premiers 
auxquels  on  ait  tente  de  dormer  des  points  fixes,  etoit  trop  difficile  a conflruire, 
pour  que  chaque  Thermometre  put  etre  gradue  immediatement.  Auffi  l’auteur 
lui-meme  n’employoit-il  fa  methode  qu’a  faire  des  etalons,  auxquels  il  ccirpa- 
roit  enfuite  les  Thermometres  defiines  aux  ufages  ordinaires.  Mr  1’ Abbe 
nollet,  ion  difciple,  qui  pendant  long  terns  a donne  le  ton  pour  les  Thermo- 
metres, taut  en  France  que  dans  les  pays  meridionaux,  fuivit  la  methods  de  fon 
maitre:  il  ne  marquoit  immediatement  fur  fes  Thermomstres,  que  le  point  de  la 
congelation;  et  il  les  comparoit  enfuite  dans  de  l’eau  a 30°  de  , cette  echelle  la, 
ou  ioo°  environ,  divifoient  l’intervalle  reel  de  la  congelation  a l’eau  bqu  ill  ante, 
Yol.  LXYIII.  O o q Par 
