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Take the difference of the tabular logarithms 
of the obferved heights of the barometer, at the 
two Nations, confidering the 4 fir ft figures (ex- 
clufive of the index) as whole numbers, and the 
three remaining figures to the right as decimals ; 
and fubftradt or add the difference of the ther- 
mometer, of a particular fcale, attached to the 
barometer, at the two ftations, according as it 
was higheft at the lower or upper ftation, and 
you will have the height of the upper ftation 
above the lower one, in Englifti fathom, nearly j 
to be corrected as follows : make this propor- 
tion ; as 1000 is to the fum of the altitudes of 
the thermometer of a particular fcale, expofed to 
the air at both ftations, fo is the height of the 
upper ftation above the lower, found nearly, to the 
corre&ion of the fame; which added or fubftradled, 
according as the fum of the altitudes of the ther- 
mometers, expofed to the air, is pofitive or ne- 
gative, will give the true height of the upper fta- 
tion above the lower in Englifh fathoms j and 
multiplied by 6 , will give it in Englifh feet. 
NEVIL MASKELYNE, 
XXI. A 
