In order to afcertain the height of Mountains. 525 
ters of an hour or more in the fame place, to acquire the 
true temperature of the air, and this before and after 
every expedition. The fra&ional parts of a degree on 
both the attached and detached thermometers were 
noted only by eftimation, but written down to ioths, 
being more convenient in the computation ; for I may 
remark, that one-third of a .degree on the attached ther- 
mometer is equal to about T5 ^ inch on the barometer; 
this attention, therefore, to the fub-divifions of the de- 
grees became neceffary. I conclude, laftly, with pre- 
fuming, that the weight (k) of any column of air may be, 
meafured with thefe barometers to ,008 inch, though all 
the errors fhould lye the fame way. . 
Leaving Geneva about half paft fix in the morning, 
Auguft 20th, I arrived at the place a of my bafe a little 
before eight; near to which there happened to.be a 
Ihepherd’s houfe, in which I left one of my barometers, 
(N° 1.) with a fervant, to examine and-obferve it every 
five or ten minutes, for near nine hours fucceflively, 
by — ,013 inch: It is difficult to account for this. May 1 oth, 1776, at Rome, 
N° 1. flood loweft by ~,ooi. June 1 2th, at Naples, N° 1. flood loweft by 
*— ,008. Sept. 10th, in London, N° 1, flood high eft by -p.006. Thefe, 
apparent variations may poftibly arife from fome, alteration in the frame-work 
of the barometers, through moiflure, &c. 
(Jk) I muft not be underftood to mean, that the length of any column of air 
may be meafured to an equal accuracy, even though our theory , fhould be pevr- 
fe£t; this will.be the fubje£l of inquiry in its proper place 0 
until 
1 , 
