[ 2 53 1 
When the abfolute elafticities are different at 
different heights, the denfities will no longer be 
proportional to the preffures ; and the change of 
denfity, throughout the whole column of the at- 
mofphere, will no longer be reprefented by any one 
logarithmic. But to fmall diftances on one fide or 
the other of different heights, it may ftill be nearly 
reprefented by parts of different logarithmics. Now 
this is really the cafe, according to M. de luc: 
for, when the temperature, at two different heights, 
hath been different, he finds, that the difference of 
thoje heights will fill be expreffed in loooths 
of a Paris toife , by the proceeding formula, viz. 
L ± ^ L, if n be under food to denote the dif- 
ference between the con ft ant temperature -j- i6f, 
and that which is the mean of the different te??ipe- 
raturcs of the two places of obfervation h) • that is to 
fay, though the temperature of that portion of the 
column of the atmofphere, which is intercepted be- 
tween the level of the two places of obfervation, 
hath not been the fame, perhaps, in any two dif- 
ferent parts ; yet the variation of denfity and height 
will be exhibited, through the whole of this final i 
fpace, without fenfibleerror, by thecurve, which would 
have reprefented them firidtly, if the entire column 
had been of the mean temperature of the extremes 
of this portion of it ; namely, by the logarithmic, 
whofe lubtangent is exprefied in loooths of a Paris 
Yl 
toife, by B — B, B denoting the fubtangent of 
the Briggian fyftem. Imagine, therefore, that the 
barometer and thermometer have been obferved at 
(i) Rechcrch. fur les Modif. de 1 ’Atm. §. 663, 
4 
the 
