( iO ) 
fon. For the Vapour which is raifed by the Winter’s 
Heat, exprefTed by the Number 2, when the Air’s . 
Rarity is 800, 'Will rife to ( and fettle at ) an Height 
of about the Sixth of a Mile, when the Barometer is 
above 30 Inches high. But if the Heat be greater 
then, the Vapours will rife higher, and pretty much 
higher if the Sun fhines, though in frofty Weather, the 
Barometer being then very high. If the Barometer 
falls, and thereby brings the Place of Equilibrium 
( for Vapours raifed by the Heat 2 ) nearer the 
Earth, then alfo will the Heat be encreafed, the Va- 
pour more rarefied, and ^onfequently the new Place 
oi Equilibrium {w^QitniXy high. It is to beobferved, 
that in Winter, when the Heat is only equal to 2, 
the Air is denfefl: clofe to the Earth, which has not 
any Heat fufficient to rarefy it near the Ground, as 
happens in warm Weather ; therefore the Vapour 
will rife gradually in an Air whofe Denfity decreafes 
continually from the Earth upwards*, neither will 
the Vapour be hindered of its full Rife, by any Con- 
denfation from a greater Cold of the ambient Air, 
the Air being then as cold next to the Ground where 
the Vapour begins to rife, as it is at any Heighth 
from the Earih. 
The Vapour which is raifed by the Heat of Spring 
or Autumn exprefied by Number 3, will rife to the 
Height of 37 Miles, when the Barometer is at 30, 
and the Air’s Rarity is 85*0. But then, as the Air 
is hotter nearer the Ground than at the Height of 
half a Mile or a Mile, the Vapour will condenfe as it 
rifes ; and as the Air, when the Earth is heated, is 
rarer near the Ground than at fome Height from it, 
the Place of Equilibrium for Vapour will, upon 
. thcfe 
