meafuring Heights with the Barometer. 699 
or r- ^ oo on a f° ot > by ai2°. Now, as the manometers re- 
ferable folid rods much more than they do barometer 
tubes, it is probable their dilatation, even allowing for the 
greater extenlion of the bulb, would not exceed -dL-ths of 
an inch on a foot, or -j^th part on every two inches. In 
this ratio I have therefore augmented the apparent, to 
obtain the true, capacity of each manometer. The equa- 
tion, amounting to about T ~th part of the whole, being 
lefs than the common error of fuch complicated obfer- 
vations, might in fail have been entirely omitted, with- 
out producing any material alteration in the refults. 
Having, in this manner, computed the total increafed 
volume of any number of equal parts of air (according 
to the capacity of the bulb and tube in grains) and very 
often likewife the partial expanlions for intermediate 
temperatures, expreffed by the contents of the corref- 
ponding fedtions of the tube, I then found the ratio 
anfwering to 1000 equal parts, which, being divided by 
the degrees of difference of temperature, gave the mean 
rate for the whole fcale, or the particular rate for any 
intermediate fedtion of it. 
The experiments, confidered in this way, are diftributed 
into four dalles, whereof the refults are comprehended 
in the four following tables. The firft Ihews the expanlion 
of air, whofe denlity was much greater than that of the 
Vo l. LXVII. 4 X 
common 
