Vyrometry  and  Arcontetry,  See.  499 
which  a greater  degree  of  exa&nefs  would  be  either 
ufelefs  or  impoflible. 
Simple  and  evident  as  this  principle  is,  yet,  as  it  often 
happens  that  obvious  ideas  do  not  ihike,  even  becaufe 
their  being  obvious  gives  them  a trivial  air,  I will 
ftrengthen  this  by  ufeful  examples,  and  one  offers  itfelf 
to  which  I have  been  led  by  the  foregoing. 
Suppofe  one  wants  to  know  the  dilatations  of  fpirit  of 
wine  by  heat,  in  order  to  have  regard  to  it  in  effaying  the 
fpirituofity  of  vinous  liquors,  which  is  wont  to  be  eftimated 
by  their  fpecific  gravities ; an  article  as  every  one  knows 
of  much  confequence  in  the  hrandy  trade,  and  which  has 
likewife  fome  connection  with  chemiftry : I fay,  that  one 
would  make  a confiderable  error  if,  in  order  to  deter- 
mine the  relations  of  the  dilatations  of  the  brandy  with 
the  indications  of  the  quickfilver  Thermometer,  which 
fhould 
plus  aifement  clans  ce  que  jc  me  propofe  de  dire  fur  ceux  ou  un^plus  grande 
exa&itude  feroit  ou  inutile  ou  impoflible. 
Quelque  Ample  et  evidente  que  foit  cette  regie,  comme  il  arrive  fouvent  que 
les  idecs  fimples  ne  frappent  point,  precifement  a caufe  de  leur  fimplicitequi  leur 
donne  un  air  trivial,  je  fortifierai  celle-ci  par  des  exemples  utiles.  Et  cn  voici 
un  d’abord,  auquel  l’exempl©  precedent  m’a  conduit. 
Je  fuppofe  qu’on  veuille  connoitre  les  dilatations  de  l’efprit  de  vin  par  la  cha- 
leur,  afin  d’y  avoir  egard  dans  la  mefure  de  la  fpirituofite  des  liqueurs  vineufes, 
eftimee  par  leur  pefanteur  fpecifique;  objet  important  au  commerce  confiderable 
des  caux  de  vie,  et  qui  intereffe  aulli  la  chimie,  Jc  dis  qu’on  feroit  un  grand 
ecart,  ii,  pour  determiner  le  rapport  des  dilatations  de  l’efprit  de  vin,  avec  les 
indications  du  Thermometre  dc  mercure,  quiferviroit  enfuite  a marquer  la  tern- 
O o o 2 peraturc 
