Pyrometry  and  Areometry , See.  521 
the  fixed  points,  in  order  to  eftablifh  an  eafy  propor- 
tion between  them,  and  the  degrees  of  the  Areometer, 
and  that  thus  one  might  make  the  correction  without 
tables.  It  would  be  eafy,  for  inftance,  to  make  the  degrees 
of  the  Thermometer  anfwer  to  quarters  of  degrees  of 
the  Areometer;  for  in  that  cafe,  reckoning  them  from 
a fixed  point,  one  would  only  have  to  correct  the  ob- 
fervations  made  upon  the  Areometer,  by  a quarter  of  the 
number  of  degrees  indicated  upon  the  Thermometer, 
which  feems  to  me  very  convenient : and  as  it  is  always 
eafier  to  add  than  to  fubtraCt,  I would  place  the  o of  this 
Thermometer  at  the  point  of  the  greateft  ordinary  heat 
of  the  air,  or  about  240  of  my  Thermometer,  and  86°  of 
Fahrenheit’s:  for  then,  reckoning  the  degrees  of  the 
Thermometer  downwards,  one  fhould  only  add  them  to 
the  indication  of  the  Areometer ; fihee  the  cooling  of  the 
liquor 
pour  qu’ils  euffent  un  rapport  fimple  avec  ceux  de  l’Areometre,  et  qu’on  put 
ainfi  fe  pafler  de  tables.  II  feroit  fort  aife,  par  exemple,  que  les  degres  du  Ther- 
mometre correfpondiffent  a des  quarts  de  degres  de  FAreometre;  et  alors,  les 
comptant  depuis  un  point  fixe,  on  n’auroit  qu’a  corriger  l’obfervation  faite  fur 
FAreometre,  par  le  quart  du  nombre  des  degres  qu’indiqueroit  le  Thermometre;, 
ce  qui  me  paroitroit  fort  commode.  Et  comme  il  eft  toujours  plus  aiie  d’addi- 
tionnerque  de  fouftraire,  je  placerois  le  zero  de  ce  Thermometre  au  point  de  la 
plus  grande  chaleur  ordinaire  de  Fair,  e’eft  a dire  aux  environs  de  24°  de  mon 
Thermometre,  ou  86°  de  Fahrenheit;  car  alors,  comptant  les  degres  du 
Thermometre  en  descendant,  il  faudroit  les  ajouter  a Findication  de  FAreome- 
Vol.  LX VIII.  R r r tre;- 
