[' 439 1 
we fhall not owe to one man alone, but to the joint 
labours of leveral. 
Account of fome of the fifi' Phenomena of the 
Humor obferved with the Hygrometer. 
75. Though my firft advances in this new track 
of obfervation are as yet very uncertain, yet I will 
not omit giving fome account of them. They will 
at leafl ferve to give fome idea of the going of the 
inffrument, as well as of the nature of the agent by 
which it is governed. 
The firff obfervation I attempted of this kind was 
with a view to one of the objedls which made me 
defirous of having an hygrometer. Thefe objedts- 
are all comprized in a general fyflem concerning 
vapours, which I have given in my work upon the 
Modifications of the Atmofphere. I (hall therefore 
only mention here one particular coniequence of that 
fyftem, which it was my immediate point to verify j 
namely, that a certain augmentation of heat, we 
always perceive at every feafon upon the approach 
of rain, is owing to a more than ordinary quantity 
of vapour; and that, on the contrary, it is to their 
diminifhed quantity that the leffer heat of the upper 
parts of the atmofphere is in great meafure to be 
afcribed. 
76. This latter confequence was fupportedby an 
accidental obfervation I made in September, 1 770, 
upon a mountain of the Faucigny, at ’the height 
of 1560 toifes above the level of the fea. An iron 
ferule, which ferved -to unite the ends of a cleft 
flick, and which had been fixed on the flick with a 
hammer 
