[ 5*5 ] 
Alembic fufficiently (hews the Operation of Heat and 
Cold on the afcending and defcending Vapour. 
Thus in a calm Evening, when there is no Wind 
to waft the Air, as the Heat of the Sun declines, the 
Cold arrefts fome few of the laft afcending Vapours, 
and, by its own Force, without any other Change 
in the State of the Air, compels them to return, in 
Dew, to the very Spot from whence they arofe; 
whilft their Brethren efcape, who go out of the 
Reach of the Cold a little before the Approach of 
Night. 
Since therefore the fame Air, in different States 
of Heat and Cold, affe&s Vapour in this Manner, it 
thence follows, that Vapour, wafted from Air of one 
Temperament to another, muft be affe&ed in the 
fame Manner alfo: So that Vapour, carried from a 
colder to a warmer Air, will afcend* and, on the 
contrary, Vapour carried from a warmer to a colder 
Air, will defcend. 
Now if Cold condenfes the Air, and thereby 
makes it prefs upon the warmers and if Vapour, 
carried by a Stream of Air from a colder to a warmer 
Region, afcends 5 we have the Reafon why the North- 
eaft blows, and why it blows dry. 
Let us fix upon fome Spot in the Continent of 
North-Europet whence this Wind comes to us: 
Suppofe Archangel , which lies on our North-eaft 
Point, and is in <S5 Degrees Northern Latitude: 
When the Froft is intenfc, the incumbent Air there 
muft needs be very heavy 5 that Air will prefs every 
Way : Qua data porta , rmt. Let us confider which 
Way this condenfed Air can burft out from thence : 
It cannot go to the North, where the Cold is greater , 
X x x 2 nor 
