[ 453 ] 
the one that remained in the (hade, the Tame upon 
which the obfervation at the mountain had been 
made, was not in fact higher than 103, though 
marked in the table of obfervations at 107 (91) 
99. But the difference between the obfervations 
made upon the mountain of Sixt, and thofe I am 
fpeaking of, was dill greater by much after fun- let. 
The 30th of Auguft, at a quarter after ten at night, 
I obferved the hygrometer without fide the cottage 
upon the mountain, and found it at 123 (79) ; and 
on the 13th of September following, in the plain, 
it was not higher than 31 at 9, and 24 at 10 o’clock.. 
The wind was fouth, and the height of the barome- 
ter upon the plain, pretty much the fame during both 
the obfervations. 
100. It is true that, notwithstanding the ftmila- 
rity of thefe circumftances, thefe obfervations cannot 
be diredtly compared, on account of the dilagree- 
ment in fome other circumftances. In the fir ft; 
place, the difference of fourteen days at this feafon 
of the year may have produced a fenfible change in 
the ftateof the air. There was already, for inftance, 
a confiderable difference in the degrees of the ther- 
mometer ; it was at 1 3 and J when the obfervation 
was made on the mountain, and no higher than at 
10 on the plain. Beftdes, at this time of night, 
there would always bean effential difference between 
the upper and lower parts of the atmofphere, even 
though in the day time they fhould have the fame 
degree of humidity : for the vapours being condenfed 
after fun-fet, and thus producing a kind of dew, 
they muft neceffarily delcend, and from this very 
caufe be more abundant in the low grounds than 
N n n 2 
on 
