[ i6 7 ] 
It may perhaps be convenient to repeat here the 
meaning of the algebraic terms, ufed in the fore- 
going formula , that any perfon may make ufe of it, 
without having occafion to recur to the foregoing 
inveftigation. B fignifies the obferved altitude of 
the barometer at the lower ftation, and b that at 
the upper ftation ; Log. B and Log. b , fignify their 
logarithms taken out of the common tables, by 
affuming the four firft figures next following the 
charadleriftic as whole numbers, and confidering the 
three remaining figures, to the right hand, as deci- 
mals; D fignifies the difference of height of Fahren- 
heit’s thermometer, attached to the barometer at 
the top and bottom of the hill; and F fignifies the 
mean of the two heights of Fahrenheit’s thermome- 
ter, expofed freely for a few minutes to the open air 
in the fbade, at the top and bottom of the hill. 
The formula , for the meafure of heights, may 
alfo be changed, and adapted to thermometers of 
particular fcales, for the convenience of calcula- 
tion, as M. de luc has done; but thefe fcales 
will be different from his. The thermometer, at- 
tached to the barometer, had better be divided 
with the interval between freezing and boiling 
water, confiding of 81,4 degrees (=180X5452) 
the freezing point may be marked o, and the 
point of boiling water will be 81,4; for then, if 
the difference of height of this thermometer, at 
the two ffations, be called d* we fhall have d — , 
0,452 x D. for d : D :: 81,4 : 180:: 0,452 : 1, and 
the number of degrees expreft by d, will fhew 
immediately the correction for the difference of 
heat of the two barometers. If the thermometer, 
defigned to ftiew the temperature of the air, be 
divided. 
