Meteorology. 505 
of the mean temperature not being able to 
support the mean quantity of vapour. 
‘This explanation’ may be: well illustrated 
by contemplating. a curve convex towards its 
axis; in which’ case the ordinates increase in 
a greater ratio than the abscisse. ‘The ab- 
scisse represent temperature, and the ordi- 
nates the quantity of steam which the cor- 
responding’ ‘temperatures are ey of re- 
Peme: 
In 1793 T published my aarp :Gtiogiedel 
Observations and Essays, ‘a few years, after 
this theory of rain had been’ made! known; 
as'far as I was then acquainted’ with it’ from 
one of the Reviews, it appeared the ‘most 
platisible of ‘any I had seen ; but’ on looking 
at my’remarks, it is’ evident I Had: not been 
made acquainted with’ its’ distinguishing fea- 
ture, and ‘that on which its excellence de- 
pends, namely, a higher solvent power (if it 
may be so called) in’ the air, than what is 
proportionate to the increasé of temperature ; 
and that the precipitation’ of ‘vapour “in: the 
form of clouds and rain is occasioned,” not 
by mere cold, ‘but: a ‘mixture’ of :compara- 
tively warm and cold air. 
At the’ tite of my’ publication of the 
Essay on Rain, &c. Thad. a strong bias to 
the opinion, that the steam or vapour in the 
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