I 
[ i6 9 ] 
at the lower or upper ftation ; and if G and I 
fhould happen to fall below o of the fcale, or to 
be fubftraCtive, they mult be applied accordingly 
in the calculation. 
I fhall now add nothing more, but to give the 
rule for finding heights by the barometer, accord- 
ing to the formula delivered above, in common 
language; firft, as adapted to Fahrenheit’s ther- 
mometer, and next, as adapted to the two ther- 
mometers of particular fcales. Take the differ- 
ence of the tabular logarithms of the obferved 
heights of the barometer, at the two fixations, 
.confidering the 4 firft figures, exclufive of the 
index, as whole numbers, and the three remain- 
ing figures to the right as decimals, and fub- 
ftraCt or add of the difference of the alti- 
tude of the Fahrenheit’s thermometer, attached to 
the barometer at the two ftations, according as it 
was h igheft at the lower or upper ftation ; thus you 
will have the height of the upper ftation above the 
lower, in Englifh fathom, nearly ; to be corrected, 
as follows : make this proportion; as 449 is to the 
difference of the mean altitude of Fahrenheit’s 
thermometer, expofed to the air at the two fta- 
tions, from 40°, fo is the height of the upper 
ftation found nearly, to the correction of the fame; 
which added or fubftraCted, according as the mean 
altitude of Fahrenheit’s thermometer was higher 
or lower than 40°, will give the true height of 
the upper ftation above the lower, in Englifh fa- 
thoms ; and multiplied by 6, will give it in Eng- 
lifh feet. 
The fame rule, adapted to the thermometers of 
particular fcales, is this : 
Vol. EXIV. Z Take 
