on  .Pyrometry  and  Areometry , Sec,  .48 1 
water  lefs  warm  upon  warmer  water,  it  was  fcarce  necef- 
fary  to  far  the  mixture : before  1 had  done  it,  the  Ther- 
mometer had  almoft  quite  fallen  to  the  point  of  the 
mean  temperature.  This  therefore  is  much  the  fafeft 
method  for  all  operations  of  this  kind.  I had  already 
experienced  it  in  the  comparifon  of  Thermometers  made 
of  different  liquors,  which  I have  mentioned  in  my  work 
above  quoted. 
By  operating  in  this  manner  I -was  fure  to  have  given 
the  rod  of  glafs  the  degree  of  heat  indicated  by  my 
Thermometer;  and  I repeat  it,  without  alluring  that 
the  numbers  above  written  give  us  the  true  law  of  the 
condenfations  of  glafs  comparatively  with  degrees  that 
are  equal  among  themfelves  upon  the  Thermometer, 
their  difference  is  too  great,  and  too  regular  not  to  point 
out  a progreffion  fenfibly  decreafing.  Here 
fur  l’eau  plus  chaude,  je  n’avois  prefque  pas  befoin  d’agiter  le  melange;  avant 
-que  je  l’euffe  fait,  le  Thermometre  avoit  bailie  prefque  entierement  au  point  de 
la  temperature  moyenne. 
C’eil  done  la  methode  la  plus  fure  de  beaucoup  pour  toutes  les  operations  de 
ce  genre.  Je  l’avois  deja  eprouve  dans  la  comparaifon  des  Thermometres  de 
differentes  liqueurs  dont  j’ai  parle  dans  mon  ouvrage  cite  ci-devant. 
En  operant  done  de  cette  maniere  j’etois  fur  d’avoir  communique  a ma 
Tranche  de  verre  la  chaleur  qu’indiquoit  mon  Thermometre.  Et  je  le  repete, 
fans  alfurerque  les  nombres  rapportes  ci-delfus  nous  donnentla  vraie  loi  des  con- 
denfations du  verre,  comparativement  a des  degres  egaux  entr’eux  fur  le  Ther- 
inometre,  leur  difference  eft  trop  grande  et  trop  reguliere,  pour  ne  pas  iadiquer 
•une  progreffion  fenliblement  decroiffante. 
Vol.  LX VIII.  M m m 
Ainli 
