Lea. VIL Salts in Water. A 30 3 
CHAP. IIL 
Wherein, from the Experiments in the foregoing Chapter, 
is /hewed, the Caufe of the Motion of the Mercury in 
the BAROMETER. E 
, OR the doing of this, it will firft be acknowledg'd, 
la That not only feveral forts of Sulphur, but alfo of 
Volatile Salts, are continually fublimed from moft 
) Bodies into the Aer. So Lightning, from the celeri- 
> ty ofthe accenfion, appears to be made of a Meteor, 
which is Nitro-Suiphureons. Snow dependeth upon 
> > a Mixture of Nitrous, and other Salts 3 as is evi- 
dent, from the regularly and differently Figur'd Parts, which compofe 
the whole Body of a Snowy Cloud, before it clufters into Flakes. And 
one reafon, why Rain is the belt Water for any Soyl, is becaufe it is im- 
prepared with divers Volatile and Fruitful Salts. And fo from otket 
Meteors. 
2. $. And next, that thefe Salts, are not always in the fame Quan- 
tity, Proportion, and State, in the Aer : but that fometimes they are 
more copious 3 at others, lef: fometimes, one more copious, than an 
other: fometimes, more plentifully diffolved 5 at others, more {pares 
ingly : and that, either as they are more or lefs pure and difloluble; or 
according to the quantity of the Vaporous Parts in the Aer, in which 
they are incorporated or diflolved, 
3. §. Thus much being granted, from the Experiments in the fore- 
roing Chapter compared together, we may refolve our felves about 
¡ome Phenomena in the Barometre. Which feems to vary, not fo much 
with the meer Weight of the Aer, which hitherto hath been fuppo- 
fed: as by the different. preflure it makes, in being crowded more at 
one time, than at another. That is, according as certain Nitrous, or 
other Saline Bodies, take up le Space in the Aer, when diflolved in the 
Watery Parts therein, than while they are undiflolved. 
4 $. And therefore it is efpecially to be obferved, That as the 
Mercury commonly rifeth in the Cylinder for fome days, but always 
for fome time, before the change of the Weather, whether for Snow or 
Rain : So, that then it prefently falleth again, even before the So 
or Rain falls. Whereas, if the Weight of the Aer, were the only, or 
the chief Canfè of the afcent of the Mercury 5 than as it rifeth all the 
while the Weather is gathering, foit would keep its ftanding or heighth, 
until the Weather breaks and falleth down: which yet it never doth, 
but always falls before it ; fometimes no lef than a whole day. The 
Canfe whereof is, in that all the while the Mercury rifeth in the Cylin- 
der, the Aer is crowded with more and more Saline Parts, which by 
po the 
