4T2.  Mr.  de  Luc  on 
the  paffage  of  water  in  ice  to  boiling  water,  that  is,  from 
0 to  80°  upon  my  Thermometer,  notwithftanding  the 
con  liberation  of  the  different  progrefs  of  quickfilver  and 
glafs  in  their  expanfions  by  heat,  which  I lhall  fpeak  of 
hereafter;  becaufe  the  two  terms  of  the  obfervation, 
1 o°  and  7 o°,  are  equi-diftant  from  the  two  fixed  points 
of  the  Thermometer.  I fhall  have  then  a third  part  to 
add  to  the  number  of  turns  for  the  expanfion  of  18 
inches  of  glafs  paffing  from  the  heat  of  water  in  ice  to 
that  of  boiling  water,  which  will  make  i o turns,  or  6~ 
for  the  expanfion  of  one  foot. 
One  turn  of  the  fcrew  being  equal  to  j^th  of  a foot, 
■ 6~  make  g~  - Tr~th  of  a foot  = f^th  of  an  inch  in  one 
foot.  Now  this  is  precifely  what  had  been  found  by 
Mr.  smeatqn.  However,  this  lingular. conformity  may 
be 
de  la  difference  des  marches  du  mercure  et  du  verre  dans  leurs  expanfions  par  la 
chaleur,  dont  je  parlerai  ci-apres : parce  que  les  deux  termes  de  robfervation, 
qui  font  iO°  et  7.0°,  fe  trouvent  iegale  diffance  de  ces  deux  points  fixes duTher* 
mometre.  J’aurai  done  un  tiers  a ajouter  ^au  nombre  des  tours,  pour  l’expan- 
fion  de  18  pouces  de  verre,  paffans  de  la  chaleur  de  l’eau  dans  la  glace  a celle  de 
Teaubouillante;  ce  qui  fera  10  tours,  ou  6§  pour  l’expanfion  d’i  pied. 
Un  tour  du  Micrometre  etant  egala  y&gv  de  pied,  6|  font  — — ~ de 
8000 
j>led  = Tens  de  pouce  dans  1 pied,  Et  voila  precifement  ce  que  Mr  smeaton 
avoit  trouve  par  fes  experiences,  Gependant  cette  conformite  finguliere  pourroit 
7 bien 
