493  Mr.  de  Luc  on 
thocl,  and  at  that  period  in  which  natural  philofophf 
was  dill  very  inaccurate,  one  did  not  obferve  the  dif- 
ference between  the  progreffions  of  fpirits  of  wine  and 
quickfilver;  and  in  fact  it  was  eafy  to  miftake  them.  I 
have  fhewn  it  in  fpeaking  of  thefe  Thermometers,  and  t 
fhall  have  occafion  to  fliew  it  more  fully  very  foon. 
This  doubtlefs  was  a defeat,  and  a very  confiderable 
one,  whether  we  confider  that  the  Thermometer  is  in- 
tended to  indicate  degrees  of  heat,  both  much  larger  and 
much  fmaller  than  the  interval  between  thefe  30°;  or 
that  it  is  a molt  capital  inftrument  in  natural  philofophy, 
and  as  fuch  may  be  ufed  in  experiments  where  the  leaft 
defeats  may  have  fenfible  confequences.  For  thefe 
reafons  I only  mention  this  cafe,  as  an  help  for  me  to 
explain  what  I propofe  to  fay  upon  other  inftruments  in 
which 
Par  cette  methode,  ct  dans  ce  terns  fa  ou  la  Phy fique  etoit  encore  fort  peu  exadte, 
«n  ne  remarquoit  pas  la  difference  des  marches  du  mercure  et  de  l’efprit  de  vin, 
k l’on  pouvoit  en  eftet  s’y  meprendre.  Jel’ai  montre  en  traitant  de  ees  Ther- 
mometres, et  je  le  montrerai  plus  partfieulierement  bientot. 
Cetoit  la  fans  doute  un  defaut,  et  un  defaut  tres  grand;  foit  parce  que  le 
Thermometre  eft  deftine  a indiquer  des  degres  de  chaleur  bien  plus  grands  et 
bren  moindres  que  l’intervalte  de  ces  30°;  foit  parce  que  e’eft  un  inftrument 
fondamental  en  Phy  fique,  qui  peut  etre  employe  a des  experiences  ou  le  moindre 
defaut  auroitdes  diets  feniibles.  Auili  ne  rapporte-je  ce  cas,  que  pour  m’expliquer 
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